3,535 research outputs found
Spin-Cherenkov effect in a magnetic nanostrip with interfacial Dzyaloshinskii-Moriya interaction
Spin-Cherenkov effect enables strong excitations of spin waves (SWs) with
nonlinear wave dispersions. The Dzyaloshinskii-Moriya interaction (DMI) results
in anisotropy and nonreciprocity of SWs propagation. In this work, we study the
effect of the interfacial DMI on SW Cherenkov excitations in permalloy
thin-film strips within the framework of micromagnetism. By performing
micromagnetic simulations, it is shown that coherent SWs are excited when the
velocity of a moving magnetic source exceeds the propagation velocity of the
SWs. Moreover, the threshold velocity of the moving magnetic source with finite
DMI can be reduced compared to the case of zero DMI. It thereby provides a
promising route towards efficient SW generation and propagation, with potential
applications in spintronic and magnonic devices.Comment: 6 pages, 5 figures. To be published in Scientific Report
Online Updating of Statistical Inference in the Big Data Setting
We present statistical methods for big data arising from online analytical
processing, where large amounts of data arrive in streams and require fast
analysis without storage/access to the historical data. In particular, we
develop iterative estimating algorithms and statistical inferences for linear
models and estimating equations that update as new data arrive. These
algorithms are computationally efficient, minimally storage-intensive, and
allow for possible rank deficiencies in the subset design matrices due to
rare-event covariates. Within the linear model setting, the proposed
online-updating framework leads to predictive residual tests that can be used
to assess the goodness-of-fit of the hypothesized model. We also propose a new
online-updating estimator under the estimating equation setting. Theoretical
properties of the goodness-of-fit tests and proposed estimators are examined in
detail. In simulation studies and real data applications, our estimator
compares favorably with competing approaches under the estimating equation
setting.Comment: Submitted to Technometric
An optical fiber tip micrograting thermometer
An ~12 µm long Bragg grating was engraved in an ~5 µm diameter optical fiber tip by focused ion beam (FIB) milling. An ~10-dB extinction was achieved at 1570 nm with only 11 indentations. The grating was used for temperature sensing, and it exhibited a temperature sensitivity of ~22 pm/°C
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