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  1. Abstract Excitonic insulators are usually considered to form via the condensation of a soft charge mode of bound electron-hole pairs. This, however, presumes that the soft exciton is of spin-singlet character. Early theoretical considerations have also predicted a very distinct scenario, in which the condensation of magnetic excitons results in an antiferromagnetic excitonic insulator state. Here we report resonant inelastic x-ray scattering (RIXS) measurements of Sr 3 Ir 2 O 7 . By isolating the longitudinal component of the spectra, we identify a magnetic mode that is well-defined at the magnetic and structural Brillouin zone centers, but which merges withmore »the electronic continuum in between these high symmetry points and which decays upon heating concurrent with a decrease in the material’s resistivity. We show that a bilayer Hubbard model, in which electron-hole pairs are bound by exchange interactions, consistently explains all the electronic and magnetic properties of Sr 3 Ir 2 O 7 indicating that this material is a realization of the long-predicted antiferromagnetic excitonic insulator phase.« less
    Free, publicly-accessible full text available December 1, 2023
  2. Owing to the increasing complexity of construction tasks and operations performed in confined workplaces, workers rely progressively on working memory, i.e., the short-term and temporary storage of information pertaining to near future events, to ensure the seamless execution of construction tasks. Although literature has discovered a strong relationship between engineering information formats and the quality of working memory, there is still a clear theoretical disagreement on the implications of the complexity of engineering information in the development of working memory. This study addresses the knowledge gap with a human-subject experiment (n=60). Participants were required to review one of the twomore »instructions for a pipe maintenance task: a simple 2D isometric drawing with bulletins (2D-simple) and a complex 2D isometric drawing with rich text (2D-complex). After the review session, the participants were asked to perform the pipe maintenance task in a Virtual Reality (VR) environment. Collected data include participants’ task performance (accuracy and time), pupillary dilations and gaze movements. The results show that the 2D-simple group outperformed the 2D-complex group in terms of both accuracy and time. An attention pattern analysis using Approximate Entropy (ApEn) of gaze movements suggests that a higher ApEn in the vertical axis, i.e. a more irregular and complex gaze movement between instructions, may result in a more efficient use of working memory and thus contributes to a better performance. This study provides preliminary evidence regarding the impact of engineering information complexity on the working memory development of construction workers.« less
  3. Owing to the increasing dynamics and complexity of construction tasks, workers often need to memorize a big amount of engineering information prior to the operations, such as spatial orientations and operational procedures. The working memory development, as a result, is critical to the performance and safety of many construction tasks. This study investigates how the format of engineering information affects human working memory based on a human-subject Virtual Reality (VR) experiment (n=90). A VR model was created to simulate a pipe maintenance task. First, participants were asked to review the task procedures in one of the following formats, including 2Dmore »isometric drawings, 3D model, and VR model. After the review session, participants were asked to perform the pipe maintenance task in the virtual environment based on their working memory. The operation accuracy and time were used as the key performance indicators of the working memory development. The experiment results indicate that the 3D and VR groups outperformed the 2D group in both operation accuracy and time, suggesting that a more immersive instruction leads to a better working memory. A further examination finds that the 2D group presented a significantly higher level of intrinsic cognitive load and extraneous cognitive load in the working memory development compared to the 3D and VR groups, indicating that different engineering information formats can cause different levels of cognitive load in working memory development, and ultimately affect the final performance. The findings are expected to inspire the design of intelligent information systems that adapt to the cognitive load of construction workers for improved working memory development.« less