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Learner autonomy has become a hot topic and goal in the research of foreign language education. However, it is the most difficult question to define language learner autonomy and any answer to it is likely to be subjective. On the basis of expounding upon the different definitions concerning the research on learner autonomy in language teaching and learning, this study was to explore how cooperative group learning helps to improve learner autonomy. The survey's findings indicate that the group work helps to improve students' learning attitude, interest and motivation. It also reveals that students' language competence and awareness of using learning resources are improved. This article discusses plausible explanations for the survey findings and makes recommendations on the roles and knowledge that language teachers should play and have to facilitate the development of learner autonomy.

Polybutene (PB) is a typical polymer with various crystal forms: I, II, III, and I′. Among them, the mechanical properties of Form I PB is better but only Form II crystal can be obtained from the melt due to the kinetic advantage and then transform to Form I slowly. While the slow phase transition rate restricts its application. Partial melting is applied to accelerate the phase transition, which was studied by Flash DSC. The results indicated that the phase transition behavior during partial melting shows dependence on the isothermal crystallization temperature and 70 °C is optimal, which can reduce the phase transition time from 20 h to 200 s. As the crystallization temperature determined, stepwise crystallization was used to accelerate the phase transition. The influence of nucleating temperature and time was investigated and the results indicated that 0 °C and 2 s are the best temperature and time, respectively. With stepwise crystallization, the phase transition time was further reduced to 50 s. Moreover, stepwise crystallization can increase the content of Form I crystal from 80.0% to 98.2%. The mechanism of phase transition during partial melting was proposed according to the results, which can supplement the existing phase transition mechanism. [ABSTRACT FROM AUTHOR]

Writing, as an advanced model of output, not only conveys the subject but also realizes the communication between readers and writers. Metadiscourse can help writers arrange and organize the discourse to influence readers' understanding of the text and their attitude towards its content. Taking writing samples of College English Test Band 4 (CET-4) as corpus, the research aims to explore the use of metadiscoure markers in high score writing group (HG) and low score writing group (LG). The research questions to be addressed in the study are as follows: 1) What are the similarities and differences between the two groups in the quantity and the types of metadiscourse markers? 2) What are the similarities and differences between the two groups in choosing metadiscourse markers? 3) What's the overall distribution of the inappropriately used metadiscourse markers in two groups? The research results show that there is a positive relation between proper use of metadiscourse markers and writing quality. This paper puts forward the strategies of improving the students' ability in the proper use of metadiscourse markers in English writing teaching.

The present paper is dedicated to the optimal time-decay estimates of global strong solutions near constant equilibrium (away from vacuum) to the compressible magnetohydrodynamic (MHD) equations in the L p critical Besov spaces. In which we claim a new low-frequency assumption that plays a key role in the large-time behavior of solutions. Precisely, we exhibit that if the low frequencies of initial data belong to some Besov space B ˙ 2 , ∞ − s 1 with s 1 ∈ (l 1 − d 2 , s 0 ] ( s 0 ≜ 2 d p − d 2 ), then the L p norm (the slightly stronger B ˙ p , 1 0 norm in fact) of strong solutions has the optimal decay t − s 1 2 − d 2 (1 2 − 1 p) ( t − d 2 p if s 1 = s 0 ) for t → ∞ , which improve the results of [Shi WX, Xu J. Large-time behavior of strong solutions to the compressible magnetohydrodynamic system in the critical framework. J Hyperbol Differ Equ. 2018;15:259–290]. The proof mainly depends on a sharp time-weighted energy estimates in light of low and high frequencies for the solutions. As a by-product, those optimal time-decay rates of B ˙ 2 , ∞ − s 1 - L r type are also captured in the critical framework. [ABSTRACT FROM AUTHOR]

In this paper, we are concerned with non-isentropic Navier–Stokes equations governing compressible viscous and heat-conductive gases. We formulate an additional regularity assumption of low frequencies in R d (d ≥ 3) and then establish the sharp time-weighted inequality, which allows us to get the time-decay estimates of global strong solutions in the Lp critical Besov spaces. Precisely, it is shown that if the initial data belong to some Besov space B ̇ 2 , ∞ − s 1 with s 1 ∈ (1 − d 2 , s 0 ] ( s 0 ≜ 2 d p − d 2 ) , then the Lp norm of the critical global solutions admits the time decay t − s 1 2 − d 2 ( 1 2 − 1 p ) (in particular, t − d 2 p if s1 = s0), which coincides with that of the heat kernel in the Lp framework. In comparison with the work of Danchin and Xu [J. Math. Fluid Mech. 20, 1641–1665 (2018)], the low-frequency assumption is improved such that the regularity s1 belongs to the whole range (1 − d 2 , s 0 ]. [ABSTRACT FROM AUTHOR]

The present work is dedicated to the well‐posedness issue of strong solutions (away from vacuum) to the compressible viscous magnetohydrodynamic (MHD) system in Rd (d  ≥  2). We aim at extending those results in previous studies to more general Lp critical framework. Precisely, by recasting the whole system in Lagrangian coordinates, we prove the local existence and uniqueness of solutions by means of Banach fixed‐point theorem. Furthermore, with the aid of effective velocity, we employ the energy argument to establish global a priori estimates, which lead to the unique global solution near constant equilibrium. Our results hold in case of small data but large highly oscillating initial velocity and magnetic field. [ABSTRACT FROM AUTHOR]