AN INVESTIGATION OF ERROR CORRECTION IN THE ZONE OF PROXIMAL DEVELOPMENT: ORAL INTERACTION WITH BEGINNING LEARNERS OF CHINESE AS A FOREIGN LANGUAGE

While most researchers acknowledge that error correction (EC) is most effective in meaningful contexts, few studies have addressed collaborative EC or longitudinal language development during oral conversations - especially conversations where new knowledge is continually integrated. By observing how the tutor helped two college-age beginning students of Chinese learn three inter-related and chronologically-offset target grammatical structures (TG) during nine weeks of hourly one-on-one tutorial sessions, the study investigated: (a) the types of assistance the tutor provided in spoken conversation; (b) changes in this assistance within and across sessions; and (c) how errors towards TG were eliminated. Analysis of protocols (transcripts marked up with visual cues), learners' questionnaires, and graphs revealed that: (a) the tutor provided two types of contingent assistance: regulation in participation (RinP), and EC on emergent errors; (b) EC was effective and its explicitness depended only on the learner's Zone of Proximal Development - same finding for RinP; (c) during the goals-oriented activity, language, serving both social (active and accurate meaning-exchange) and cognitive (tutor's EC and RinP, and learners' meta-comments) functions, was responsible for learners' transformation from other-regulation to self-regulation - language serving a cognitive function on an inter-personal level gradually became intra-personal; (d) RinP was instrumental in transferring not only the responsibility for participation (elaboration, initiation, and elicitation of TG) but also, through EC consequent to elicitation of TG, the responsibility for grammar-accuracy; and, (e) TG lacking an English counterpart required not only learners' cognitive understanding of the TG form but also where (which contexts) to use it - here, RinP efficiently co-constructed contexts for elicitation of TG and its differentiation, through EC. In line with Vygostkian principles, the tutor's collaborative RinP improved learners' participation while the collaborative EC improved the learners' grammar accuracy within that improving participation. Implications include: (a) grammar accuracy is not an end-product but depended on not only task-difficulty and subject-matter but also degree to which similar TG were differentiated; and, (b) all errors, salient and not, must be corrected from the beginning - ignoring errors deemed "unimportant" was myopic

Stability analysis of the five-dimensional energy demand-supply system

summary:In this paper, a five-dimensional energy demand-supply system has been considered. On the one hand, we analyze the stability for all of the equilibrium points of the system. For each of equilibrium point, by analyzing the characteristic equation, we show the conditions for the stability or instability using Routh-Hurwitz criterion. Then numerical simulations have been given to illustrate all of cases for the theoretical results. On the other hand, by introducing the phenomenon of time delay, we establish the five-dimensional energy demand-supply model with time delay. Then we analyze the stability of the equilibrium points for the delayed system by the stability switching theory. Especially, Hopf bifurcation has been considered by showing the explicit formulae using the central manifold theorem and Poincare normalization method. For each cases of the theorems including the Hopf bifurcation, numerical simulations have been given to illustrate the effectiveness of the main results

A single radio-emitting nucleus in the dual AGN candidate NGC 5515

The Seyfert galaxy NGC 5515 has double-peaked narrow-line emission in its optical spectrum, and it has been suggested that this could indicate that it has two active nuclei. We observed the source with high resolution Very Long Baseline Interferometry (VLBI) at two radio frequencies, reduced archival Very Large Array data, and re-analysed its optical spectrum. We detected a single, compact radio source at the position of NGC 5515, with no additional radio emission in its vicinity. The optical spectrum of the source shows that the blue and red components of the double-peaked lines have very similar characteristics. While we cannot rule out unambiguously that NGC 5515 harbours a dual AGN, the assumption of a single AGN provides a more plausible explanation for the radio observations and the optical spectrum.Comment: 6 pages, 1 figure, accepted for publication in MNRA

Full-range Gate-controlled Terahertz Phase Modulations with Graphene Metasurfaces

Local phase control of electromagnetic wave, the basis of a diverse set of applications such as hologram imaging, polarization and wave-front manipulation, is of fundamental importance in photonic research. However, the bulky, passive phase modulators currently available remain a hurdle for photonic integration. Here we demonstrate full-range active phase modulations in the Tera-Hertz (THz) regime, realized by gate-tuned ultra-thin reflective metasurfaces based on graphene. A one-port resonator model, backed by our full-wave simulations, reveals the underlying mechanism of our extreme phase modulations, and points to general strategies for the design of tunable photonic devices. As a particular example, we demonstrate a gate-tunable THz polarization modulator based on our graphene metasurface. Our findings pave the road towards exciting photonic applications based on active phase manipulations

The Impact of Covid-19 on the Global Stock Market and the Global Retail Industry

The Covid-19 outbreak had a profound impact on the development of global integration. Therefore, it becomes particularly critical to explore the impact of the pandemic on the global economy and some specific industries, such as retailing. This study investigates the relationship between stock indexes and some macroeconomic indicators in 25 countries using Vector Autoregression (VAR) models. According to the Granger Causality Test, the stock indexes and macroeconomic indicators were closely connected in most countries. The price of crude oil and the stock index is the most correlated, showing a negative correlation. Meanwhile, the VAR model shows that the development of pandemics suppresses the stock market index of most countries through the increase of Covid-19 and the mortality rate. In addition, this study analyzes the stock prices of nearly 2,000 public retailing companies in the short term and one-year post-pandemic time through the Event Study Methodology (ESM) approach. We find that in the short term, the pandemic severely hits the retail industry in most countries and then gradually decays to a lower level over time. At the same time, the impact of the pandemic is lagged and long-term for the retail sector in other countries. Moreover, the pandemic has the most significant adverse effects on apparel-related retailing and the most negligible impact on food-related retailing. This is primarily due to the lockdown policy and shifting consumer demand. In addition, online-related retailers witnessed significant market share growth during the pandemic. Although offline retailers were severely shocked by the pandemic, their recovery gained remarkable momentum as the lockdown policy was terminated and the government managed the outbreak

BEDRF: Bidirectional Edge Diffraction Response Function for Interactive Sound Propagation

We introduce bidirectional edge diffraction response function (BEDRF), a new approach to model wave diffraction around edges with path tracing. The diffraction part of the wave is expressed as an integration on path space, and the wave-edge interaction is expressed using only the localized information around points on the edge similar to a bidirectional scattering distribution function (BSDF) for visual rendering. For an infinite single wedge, our model generates the same result as the analytic solution. Our approach can be easily integrated into interactive geometric sound propagation algorithms that use path tracing to compute specular and diffuse reflections. Our resulting propagation algorithm can approximate complex wave propagation phenomena involving high-order diffraction, and is able to handle dynamic, deformable objects and moving sources and listeners. We highlight the performance of our approach in different scenarios to generate smooth auralization