David R. Smith

TL;DR: This work presents an edge detector able to detect obstacles at 15 different locations with an average efficiency of 97% and minimal crosstalk and calls this class of devices that can integrate a vast number of distinct optical functions with high efficiency symphotic.

TL;DR: Initial comparisons of laser tracker, holography and photogrammetry measurements taken in 2015 are presented, showing clearly the status of alignment for distinct zones of the currently operating 32.5 m primary collecting area.

Abstract: We implement unsupervised machine learning techniques to identify characteristic evolution patterns and associated parameter regimes in edge localized mode (ELM) events observed on the National Spherical Torus Experiment. Multi-channel, localized measurements spanning the pedestal region capture the complex evolution patterns of ELM events on Alfven timescales. Some ELM events are active for less than 100 μs, but others persist for up to 1 ms. Also, some ELM events exhibit a single dominant perturbation, but others are oscillatory. Clustering calculations with time-series similarity metrics indicate the ELM database contains at least two and possibly three groups of ELMs with similar evolution patterns. The identified ELM groups trigger similar stored energy loss, but the groups occupy distinct parameter regimes for ELM-relevant quantities like plasma current, triangularity, and pedestal height. Notably, the pedestal electron pressure gradient is not an effective parameter for distinguishing the ELM groups, but the ELM groups segregate in terms of electron density gradient and electron temperature gradient. The ELM evolution patterns and corresponding parameter regimes can shape the formulation or validation of nonlinear ELM models. Finally, the techniques and results demonstrate an application of unsupervised machine learning at a data-rich fusion facility.

TL;DR: In this article, the design method for complex electromagnetic materials is expanded from form-invariant coordinate transformations of Maxwell's equations to finite embedded coordinate transformations, which allow the transfer of electromagnetic field manipulations from the transformation-optical medium to another medium, thereby allowing the design of structures that are not exclusively invisible.

TL;DR: In this article, the applications of metamaterials to lenses with a negative index of refraction were described and a detailed map of the focal region of the lenses was made.