Second-order solutions for random interfacial waves in N-layer density-stratified fluid with steady uniform currents

In the present paper, the random inter facial waves in N-layer density-stratified fluids moving at different steady uniform speeds are researched by using an expansion technique, and the second-order a symptotic solutions of the random displacements of the density interfaces and the associated velocity potentials in N-layer fluid are presented based on the small amplitude wave theory. The obtained results indicate that the wave-wave second-order nonlinear interactions of the wave components and the second-order nonlinear interactions between the waves and currents are described. As expected, the solutions include those derived by Chen (2006) as a special case where the steady uniform currents of the N-layer fluids are taken as zero, and the solutions also reduce to those obtained by Song (2005) for second-order solutions for random interfacial waves with steady uniform currents if N=2.

Second-order Stokes wave solutions for intefacial waves in three-layer stratified fluid with background current

In this paper, interfacial waves in three-layer stratified fluid with background current are investigated using a perturbation method, and the second-order asymptotic solutions of the velocity potentials and the second-order Stokes wave solutions of the associated elevations of the interfacial waves are presented based on the small amplitude wave theory, and the Kelvin-Helmholtz instability of interfacial waves is studied. As expected, for three-layer stratified fluid with background current, the first-order asymptotic solutions (linear wave solutions), dispersion relation and the second-order asymptotic solutions derived depend on not only the depths and densities of the three-layer fluid but also the background current of the fluids, and the second-order Stokes wave solutions of the associated elevations of the interfacial waves describe not only the second-order nonlinear wave-wave interactions between the interfacial waves but also the second-order nonlinear interactions between the interfacial waves and currents. It is also noted that the solutions obtained from the present work include the theoretical results derived by Chen et al (2005) as a special case. It also shows that with the given wave number k (real number) the interfacial waves may show Kelvin-Helmholtz instability.

学习不良儿童的元认知偏差及矫正

Metacognitive illusions or metacognitive bias is a concept that is a homologous with metacognitve monitor accuracy. In the dissertation, metacognitive illusions mainly refers to the absolute differences between judgment of learning (JOL) and recall because individuals are misguided by some invalid cues or information. JOL is one kind of metacognitive judgments, which is the prediction about the future performance of learned materials. Its mechanism and accuracy are the key issues in the study of JOL. Cue-utilization framework proposed by Koriat (1997) summarized the previous findings and provided a significant advance in understanding how people make JOL. However, the model is not able to explain individual differences in the accuracy of JOL. From the perspective of people’s cognitive bound, our study use posterior associative word pairs easy to produce metacognitive bias to explore the deeper psychological mechanism of metacontive bias. Moreover, we plan to investigate the cause to result in higher metacognitive illusions of children with LD. Based on these, the study tries to look for the method of mending metacognitive illusions. At the same time, we will summarize the findings of this study and previous literatures, and propose a revesied theory for explaining children’s with LD cue selection and utilization according to Koriat’s cue-utilization model. The results of the present study indicated that: (1) Children showed stable metacognitive illusions for the weak associative and posterior associative word pairs, it was not true for strong associative word pairs. It was higher metacognitive illusions for children with LD than normal children. And it was significant grade differences for metacognitive illusions. A priori associative strength exerted a weaker effect on JOL than it did on recall. (2) Children with LD mainly utilized retrieval fluency to make JOL across immediate and delay conditions. However, for normal children, it showed some distinction between encoding fluency and retrieval fluency as potential cues for JOL across immediate and delay conditions. Obviously, children with LD lacked certain flexibility for cue selection and utilization. (3)When word pairs were new list, it showed higher metacognitve transfer effects for analytic inferential group than heuristic inferential group for normal children in the second block. And metacognitive relative accuracy got increased for both children with and without LD across the experimental conditions. However, it was significantly improved only for normal children in analytic inferential group.