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The study is designed to examine the effectiveness of corrective feedback (CF) from Chinese second language (L2) teachers to their students in mainland China. Investigations into how CF works were carried out based on three aspects: teachers' perceptions of CF effectiveness, factors affecting it, and their interplay. An ecological approach--the nested ecosystem model--was employed to analyze data collected from interviews and stimulated recall interviews. A total of 22 class periods from 11 teachers were observed, and 8 teachers were interviewed. Collected data were then analyzed with Nvivo 11. Findings suggest that teachers' main criterion for effective CF is raising students' awareness of the error. Factors affecting teachers' perceptions of CF effectiveness can be direct or indirect. Direct factors refer to the manner of CF provision, which was determined by reasons including error, teaching focus, audience, learners' individual difference, teaching experience and class time. Indirect factors include empathy, cultural stereotypes and learners' emotions. The influence of each individual factor on CF effectiveness, as well as the influence of their interplay, was examined. This study suggests that in the context of mainland China, teachers' perceptions of effective CF were based on raising students' awareness on the error; factors affecting CF effectiveness were largely the same as those in previous studies. What is new to the current study is that it highlights the influence of indirect factors from cultural and affective dimensions on teachers' CF perceptions and the dynamic nature of CF effectiveness.

GeTe has been considered as a promising mid‐temperature thermoelectric (TE) candidate, but its zT value is severely limited by the excessive hole concentration and high thermal conductivity. Here, it is demonstrated that the TE properties of GeTe can be significantly improve by defect engineering of Sb‐Pb and AgCuTe codoping. The Sb‐Pb codoping is adopted to optimize the carrier concentration and manipulate the rhombohedral lattice distortion, leading to valence band convergence and enhanced power factor. The AgCuTe alloying introduces multiscale phonon scattering centers including dislocations and nano‐precipitates to reduce the lattice thermal conductivity in GeTe. Consequently, a maximum zT of 2.3 at 773 K and an average zT of 1.43 (300–773 K) are obtained in (Ge0.84Sb0.06Pb0.1Te)0.99(AgCuTe)0.01. Moreover, the fabricated thermoelectric module exhibits a high output power density of 0.59 W cm–2 and an energy conversion efficiency of 7.9% at ΔT = 500 K, suggesting hierarchical defect engineering is an effective strategy to realize high‐performance GeTe‐based thermoelectric. [ABSTRACT FROM AUTHOR]

By engineering chemically identical but structurally distinct materials into intricate and sophisticated polytypic nanostructures, which often surpass their pure phase objects and even produce novel physical and chemical properties, exciting applications in the fields of photovoltaics, electronics and photocatalysis can be achieved. In recent decades, various methods have been developed for synthesizing a library of polytypic nanocrystals encompassing IV, III–V and II–VI polytypic semiconductors. The exceptional performances of polytypic metal chalcogenide nanocrystals have been observed, making them highly promising candidates for applications in photonics and electronics. However, achieving high-precision control over the morphology, composition, crystal structure, size, homojunctions, and periodicity of polytypic metal chalcogenide nanostructures remains a significant synthetic challenge. This review article offers a comprehensive overview of recent progress in the synthesis and control of polytypic metal chalcogenide nanocrystals using colloidal synthetic strategies. Starting from a concise introduction on the crystal structures of metal chalcogenides, the subsequent discussion delves into the colloidal synthesis of polytypic metal chalcogenide nanocrystals, followed by an in-depth exploration of the key factors governing polytypic structure construction. Subsequently, we provide comprehensive insights into the physical properties of polytypic metal chalcogenide nanocrystals, which exhibit strong correlations with their applications. Thereafter, we emphasize the significance of polytypic nanostructures in various applications, such as photovoltaics, photocatalysis, transistors, thermoelectrics, stress sensors, and the electrocatalytic hydrogen evolution. Finally, we present a summary of the recent advancements in this research field and provide insightful perspectives on the forthcoming challenges, opportunities, and future research directions. [ABSTRACT FROM AUTHOR]

Bi2Te3‐based alloys have historically dominated the commercial realm of near room‐temperature thermoelectric (TE) materials. However, the more widespread application is currently constrained by its mediocre TE performance and inferior mechanical properties resulting from intrinsic hierarchical structure. Herein, microstructure modulation and carrier transport optimization strategies are employed to efficiently balance the electro‐thermal transport performance. Specifically, the weighted mobility increases by 24%, while the lattice thermal conductivity decreases by 31% at 350 K compared to the matrix. Consequently, the Bi0.5Sb1.496Cu0.004Te2.98 sample attains a peak ZT of 1.45 at 350 K and an average ZT of 1.20 (300–500 K). Moreover, intricated microstructure design, exemplified by the gradient twin structure, significantly enhances the mechanical performance metrics, including Vickers hardness, compressive strength, and bending strength, to notable levels of 0.94 GPa, 224 MPa, and 58 MPa, respectively. Consequently, the constructed 17‐pair TE modules demonstrate a maximum conversion efficiency of 6.5% at ΔT = 200 K, surpassing the majority of reported Bi2Te3‐based modules. This study provides novel insights into the synergistic enhancement of TE and mechanical properties in Bi2Te3‐based materials, with potential applicability to other TE systems. [ABSTRACT FROM AUTHOR]

As a benchmark for commercial room-temperature thermoelectric (TE) materials, the widespread demand for recovering distributed low-grade waste heat (below 573 K) underscores the immediate necessity for advanced Bi2Te3-based alloys. Here, we achieved a 22% enhancement of the peak ZT to 1.43 at 325 K by incorporating highly reactive additive Cu2SnTe3 into Bi0.5Sb1.5Te3, which is notably higher than that of most BixSb2−xTe3-based composites. This remarkable enhancement is facilitated by the in situ reaction of decomposition products with the matrix, thereby boosting hole concentration and the density-of-states effective mass, while experiencing little loss in hole mobility. Simultaneously, the lattice thermal conductivity is significantly reduced by multiscale scattering sources, typical of dislocation arrays and Sb and Cu-rich nanoprecipitates. These synergistic results yield a 30% enhancement of the TE quality factor at 300 K, reaching 0.52 for the optimal Bi0.5Sb1.5Te3 + 0.08 wt% Cu2SnTe3 sample. More significantly, when coupled with n-type zone-melted Bi2Te2.7Se0.3, the well-designed 17-pair TE module achieves a conversion efficiency of ∼6.0%, surpassing the majority of reported Bi2Te3-based modules, which further demonstrates the efficacy of the Cu2SnTe3 compositing strategy and the great potential for practical applications. [ABSTRACT FROM AUTHOR]

Power generation modules utilizing thermoelectric (TE) materials are suitable for recycling widespread low‐grade waste heat (<600 K), highlighting the immediate necessity for advanced Bi2Te3‐based alloys. Herein, the substantial enhancement in TE performance of the p‐type Bi0.4Sb1.6Te3 (BST) sintered sample is realized by subtly incorporating the non‐stoichiometric Ag5Te3 and counteractive Se. Specifically, Ag atoms diffused into the BST lattice improve the density‐of‐states effective mass (md*) and boost the hole concentration for the suppressed bipolar effect. The addition of Se further improves md* prompting the room‐temperature power factor upgrade to 46 W cm−1 K−2. Concurrently, the lattice thermal conductivity is considerably lowered by multiple scattering sources exemplified by Sb‐rich nanoprecipitates and dense dislocations. These synergistic results yield a high peak ZT of 1.44 at 375 K and an average ZT of 1.28 between 300 and 500 K in the Bi0.4Sb1.6Te2.95Se0.05 + 0.05 wt.% Ag5Te3 sample. More significantly, when coupled with n‐type zone‐melted Bi2Te2.7Se0.3, the integrated 17‐pair TE module achieves a competitive conversion efficiency of 6.1% and an output power density of 0.40 W cm−2 at a temperature difference of 200 K, demonstrating great potential for practical applications. [ABSTRACT FROM AUTHOR]

Methods to map radiofrequency (RF) field generated by an RF coil/pulse have been developed. By measuring the changes of RF field in biological tissues when an RF pulse passing through, the electrical properties of the tissue could be retrieved and used for early diagnosis of diseases such as cancer. So far, RF field mapping is mainly done for birdcage coils at high fields. Less research has been performed on phased array coils at low fields. This work studied how loading would affect the distribution of RF field in low-field MRI with permanent magnet (i.e., 17.8 MHz). Both finite element simulation and experimental results demonstrated that coil loading changed the uniformity of RF field significantly, and the distortion of RF field under the loaded condition could reflect the electrical characteristics of the loaded biological tissues.