1,038 research outputs found
Three-dimensional wakes in linearly stratified liquids.
Massachusetts Institute of Technology. Dept. of Civil Engineering. Thesis. 1966. M.S.MICROFICHE COPY ALSO AVAILABLE IN BARKER ENGINEERING LIBRARY.Bibliography: p. 80.M.S
Achromatic shearing phase sensor for generating images indicative of measure(s) of alignment between segments of a segmented telescope's mirrors
An achromatic shearing phase sensor generates an image indicative of at least one measure of alignment between two segments of a segmented telescope's mirrors. An optical grating receives at least a portion of irradiance originating at the segmented telescope in the form of a collimated beam and the collimated beam into a plurality of diffraction orders. Focusing optics separate and focus the diffraction orders. Filtering optics then filter the diffraction orders to generate a resultant set of diffraction orders that are modified. Imaging optics combine portions of the resultant set of diffraction orders to generate an interference pattern that is ultimately imaged by an imager
Electrochemistry in supercritical fluids
A wide range of supercritical fluids (SCFs) have been studied as solvents for electrochemistry with carbon dioxide and hydrofluorocarbons (HFCs) being the most extensively studied. Recent advances have shown that it is possible to get well-resolved voltammetry in SCFs by suitable choice of the conditions and the electrolyte. In this review, we discuss the voltammetry obtained in these systems, studies of the double-layer capacitance, work on the electrodeposition of metals into high aspect ratio nanopores and the use of metallocenes as redox probes and standards in both supercritical carbon dioxide–acetonitrile and supercritical HFCs
Sharpness-Aware Minimization and the Edge of Stability
Recent experiments have shown that, often, when training a neural network
with gradient descent (GD) with a step size , the operator norm of the
Hessian of the loss grows until it approximately reaches , after which
it fluctuates around this value. The quantity has been called the
"edge of stability" based on consideration of a local quadratic approximation
of the loss. We perform a similar calculation to arrive at an "edge of
stability" for Sharpness-Aware Minimization (SAM), a variant of GD which has
been shown to improve its generalization. Unlike the case for GD, the resulting
SAM-edge depends on the norm of the gradient. Using three deep learning
training tasks, we see empirically that SAM operates on the edge of stability
identified by this analysis
The Dynamics of Sharpness-Aware Minimization: Bouncing Across Ravines and Drifting Towards Wide Minima
We consider Sharpness-Aware Minimization (SAM), a gradient-based optimization
method for deep networks that has exhibited performance improvements on image
and language prediction problems. We show that when SAM is applied with a
convex quadratic objective, for most random initializations it converges to a
cycle that oscillates between either side of the minimum in the direction with
the largest curvature, and we provide bounds on the rate of convergence.
In the non-quadratic case, we show that such oscillations effectively perform
gradient descent, with a smaller step-size, on the spectral norm of the
Hessian. In such cases, SAM's update may be regarded as a third derivative --
the derivative of the Hessian in the leading eigenvector direction -- that
encourages drift toward wider minima.Comment: 30 page
Orientation and symmetry control of inverse sphere magnetic nanoarrays by guided self-assembly
Inverse sphere shaped Ni arrays were fabricated by electrodeposition on Si through the guided self-assembly of polystyrene latex spheres in Si/SiO2 patterns. It is shown that the size commensurability of the etched tracks is critical for the long range ordering of the spheres. Moreover, noncommensurate guiding results in the reproducible periodic triangular distortion of the close packed self-assembly. Magnetoresistance measurements on the Ni arrays were performed showing room temperature anisotropic magnetoresistance of 0.85%. These results are promising for self-assembled patterned storage media and magnetoresistance devices
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