Threshold concept knowledge in analogue electronics: Support and assessment

In electrical engineering, as in other academic disciplines, there exist special, threshold concepts, where students often get stuck but which once grasped reveal new ways of thinking about a subject. Two surveys, student interviews and focus group discussions, and students’ assessment were directed at learning of threshold concepts and their pre-cursors. Results suggest that one of the precursor concepts, current flow, may be a threshold concept in itself. A model of precursor and threshold concepts assessment and additional student-support for learning threshold concepts is suggested

Understanding Visual Feedback in Large-Display Touchless Interactions: An Exploratory Study

Touchless interactions synthesize input and output from physically disconnected motor and display spaces without any haptic feedback. In the absence of any haptic feedback, touchless interactions primarily rely on visual cues, but properties of visual feedback remain unexplored. This paper systematically investigates how large-display touchless interactions are affected by (1) types of visual feedback—discrete, partial, and continuous; (2) alternative forms of touchless cursors; (3) approaches to visualize target-selection; and (4) persistent visual cues to support out-of-range and drag-and-drop gestures. Results suggest that continuous was more effective than partial visual feedback; users disliked opaque cursors, and efficiency did not increase when cursors were larger than display artifacts’ size. Semantic visual feedback located at the display border improved users’ efficiency to return within the display range; however, the path of movement echoed in drag-and-drop operations decreased efficiency. Our findings contribute key ingredients to design suitable visual feedback for large-display touchless environments.This work was partially supported by an IUPUI Research Support Funds Grant (RSFG)

The interactional work of configuring a mathematical object in a technology-enabled embodied learning environment

We present a detailed account of interactional mechanisms that support participation in STEM disciplinary practices as an adult and a child explore a technology-enabled embodied learning environment for mathematics. Drawing on ethnomethodological studies of technologyrich workplaces, we trace the process of transforming a vague reference into a mutually available mathematical object: a covariant variable. Our analysis reveals that this mathematical object is an interactional achievement, configured via a reciprocal process of instructing one another's attention. In particular, we demonstrate how participants' explicit responsiveness to indexical and multimodal resources achieves this object

Multiple Sub-Jet Model of Gamma Ray Bursts and Possible Origin of X-ray Precursors and Post-cursors

We assume that internal shocks of Gamma Ray Bursts (GRBs) consist of multiple sub-jets with a collimation half-angle $\sim {\rm several }\times\gamma_i^{-1}$, where $\gamma_i$ is the Lorenz factor of each sub-jet. If by chance a sub-jet is first emitted off-axis from the line of sight, the observed peak energy can be in the X-ray region. Next if by chance a subsequent sub-jet is emitted along the line of sight, then the peak energy will be in the gamma ray region and the gamma ray may arrive after the X-ray precursor from the former sub-jet depending on parameters. This model predicts a new class of GRBs with extremely weak and short gamma ray emission but X-ray precursor and/or post-cursor as well as an afterglow.Comment: 6 pages, Latex, accepted for publication in Astrophysical Journal Letter

Study of the spectral properties of ELM precursors by means of wavelets

The high confinement regime (H-mode) in tokamaks is accompanied by the occurrence of bursts of MHD activity at the plasma edge, so-called edge localized modes (ELMs), lasting less than 1 ms. These modes are often preceded by coherent oscillations in the magnetic field, the ELM precursors, whose mode numbers along the toroidal and the poloidal directions can be measured from the phase shift between Mirnov pickup coils. When the ELM precursors have a lifetime shorter than a few milliseconds, their toroidal mode number and their nonlinear evolution before the ELM crash cannot be studied reliably with standard techniques based on Fourier analysis, since averaging in time is implicit in the computation of the Fourier coefficients. This work demonstrates significant advantages in studying spectral features of the short-lived ELM precursors by using Morlet wavelets. It is shown that the wavelet analysis is suitable for the identification of the toroidal mode numbers of ELM precursors with the shortest lifetime, as well as for studying their nonlinear evolution with a time resolution comparable to the acquisition rate of the Mirnov coils