Enhancing Grammar Learning with a Multimedia Instructional Module:Design and Teaching of“Shì...de”Construction for CFL learners

This pilot study examined the effectiveness and students’perceptions of a multimedia module on intermediate Chinese-as-a-Foreign-Language(CFL)learners’understanding and use of the“shì...de”construction.The module was designed based on the First Principles of Instruction(Morrill,2002)and the Cognitive Theory of Multimedia Learning(Mayer,2009;2014).It provided a systematic and comprehensive approach to teaching the“shì...de”construction,one of the most challenging grammar points in CFL.Twenty-two CFL learners participated in this mixed-methods study.Data were collected using pre-and post-tests,a survey,think-alouds,and semi-structured interviews.Findings show that after using the module,students’understanding and use of the construction significantly improved,except for their understanding of the second usage.The students enjoyed using the module and appreciated how it was designed,the way it was presented,and its availability.The reasons for the effectiveness of the module were analyzed and led to suggested improvements to the design of the module.The detailed description of the design process and the research result contribute to the knowledge of designing grammar teaching modules with multimedia for online,blended,and flipped learning.

Differentiated design strategies toward broadband achromatic and polarizationinsensitive metalenses

Metasurfaces have emerged as a flexible platform for shaping the electromagnetic field via the tailoring phase,amplitude,and polarization at will.However,the chromatic aberration inherited from building blocks’diffractive nature plagues them when used in many practical applications.Current solutions for eliminating chromatic aberration usually rely on searching through many meta-atoms to seek designs that satisfy both phase and phase dispersion preconditions,inevitably leading to intensive design efforts.Moreover,most schemes are commonly valid for incidence with a specific spin state.Here,inspired by the Rayleigh criterion for spot resolution,we present a design principle for broadband achromatic and polarization-insensitive metalenses using two sets of anisotropic nanofins based on phase change material Ge2Sb2Se4Te1.By limiting the rotation angles of all nanofins to either 0 deg or 90 deg,the metalens with a suitable numerical aperture constructed by this fashion allows for achromatic and polarization-insensitive performance across the wavelength range of 4–5μm,while maintaining high focusing efficiency and diffraction-limited performance.We also demonstrate the versatility of our approach by successfully implementing the generation of broadband achromatic and polarization-insensitive focusing optical vortex.This work represents a major advance in achromatic metalenses and may find more applications in compact and chip-scale devices.