Simplified Neural Unsupervised Domain Adaptation

Unsupervised domain adaptation (UDA) is the task of modifying a statistical model trained on labeled data from a source domain to achieve better performance on data from a target domain, with access to only unlabeled data in the target domain. Existing state-of-the-art UDA approaches use neural networks to learn representations that can predict the values of subset of important features called "pivot features." In this work, we show that it is possible to improve on these methods by jointly training the representation learner with the task learner, and examine the importance of existing pivot selection methods.Comment: To be presented at NAACL 201

GEOSIM: A numerical model for geophysical fluid flow simulation

A numerical model which simulates geophysical fluid flow in a wide range of problems is described in detail, and comparisons of some of the model's results are made with previous experimental and numerical studies. The model is based upon the Boussinesq Navier-Stokes equations in spherical coordinates, which can be reduced to a cylindrical system when latitudinal walls are used near the pole and the ratio of latitudinal length to the radius of the sphere is small. The equations are approximated by finite differences in the meridional plane and spectral decomposition in the azimuthal direction. The user can specify a variety of boundary and initial conditions, and there are five different spectral truncation options. The results of five validation cases are presented: (1) the transition between axisymmetric flow and baroclinic wave flow in the side heated annulus; (2) the steady baroclinic wave of the side heated annulus; (3) the wave amplitude vacillation of the side heated annulus; (4) transition to baroclinic wave flow in a bottom heated annulus; and (5) the Spacelab Geophysical Fluid Flow Cell (spherical) experiment

Basic studies of baroclinic flows

A fully nonlinear 3-dimensional numerical model (GEOSIM), previously developed and validated for several cases of geophysical fluid flow, has been used to investigate the dynamical behavior of laboratory experiments of fluid flows similar to those of the Earth's atmosphere. The phenomena investigated are amplitude vacillation, and the response of the fluid system to uneven heating and cooling. The previous year's work included hysteresis in the transition between axisymmetric and wave flow. Investigation is also continuing of the flows in the Geophysical Fluid Flow Cell (GFFC), a low-gravity Spacelab experiment. Much of the effort in the past year has been spent in validation of the model under a wide range of external parameters including nonlinear flow regimes. With the implementation of a 3-dimensional upwind differencing scheme, higher spectral resolution, and a shorter time step, the model has been found capable of predicting the majority of flow regimes observed in one complete series of baroclinic annulus experiments of Pfeffer and co-workers. Detailed analysis of amplitude vacillation has revealed that the phase splitting described in the laboratory experiments occurs in some but not all cases. Through the use of animation of the models output, a vivid 3-dimensional view of the phase splitting was shown to the audience of the Southeastern Geophysical Fluid Dynamics Conference in March of this year. A study on interannual variability was made using GEOSIM with periodic variations in the thermal forcing. Thus far, the model has not predicted a chaotic behavior as observed in the experiments, although there is a sensitivity in the wavenumber selection to the initial conditions. Work on this subject, and on annulus experiments with non-axisymmetric thermal heating, will continue. The comparison of GEOSIM's predictions will result from the Spacelab 3 GFFC experiments continued over the past year, on a 'back-burner' basis. At this point, the study (in the form of a draft of a journal article) is nearly completed. The results from GEOSIM compared very well with the experiments, and the use of the model allows the demonstration of flow mechanics that were not possible with the experimental data. For example, animation of the model output shows that the forking of the spiral bands is a transient phenomenon, due to the differential east-west propagation of convection bands from different latitudes

On the Spatial Distribution of Hard X-Rays from Solar Flare Loops

The aim of this paper is to investigate the spatial structure of the impulsive phase hard X-ray emission from solar flares. This work is motivated by the YOHKOH and the forthcoming HESSI observations. Summarizing past results, it is shown that the transport effects can account for the observations by inhomogeneous loops where there is a strong field convergence and/or density enhancement at the top of the flaring loop. Scattering by plasma turbulence at the acceleration site or pancake type pitch angle distribution of the accelerated electrons can also give rise to enhanced emission at the loop tops. These could be a natural consequence of acceleration by plasma waves. This paper considers a general case of stochastic scattering and acceleration that leads to an isotropic pitch angle distribution and an enhanced emission from the loop tops or the acceleration site. Following the formalism developed in earlier papers the strength and the spectrum of the radiation expected from the acceleration site and the foot points are evaluated and their dependence on the parameters describing the acceleration process and the flare plasma are determined. The theoretical ratio of these two intensities and relative values of their spectral indices are compared with the YOHKOH observations, demonstrating that the above mentioned parameters can be constrained with such observations. It is shown that future high spatial and spectral resolution observations, for example those expected from HESSI, can begin to distinguish between different models and constrain their parameters.Comment: 37 pages with 20 figures. Accepted for publication in ApJ http://www.astronomy.stanford.ed

The ATLAS Series of Shuttle Missions

The ATLAS space shuttle missions were conducted in March 1992, April 1993, and November 1994. The ATLAS payload and companion instruments made measurements of solar irradiance and middle atmospheric temperatures and trace gas concentrations. The solar irradiance measurements included total and spectrally resolved solar irradiance. The atmospheric measurements included microwave, infrared, and ultraviolet limb sounding, nadir ultraviolet backscatter, and solar occultation techniques. This paper introduces a special section in this issue of Geophysical Research Letters

LCF Life of NiCr-Y Coated Disk Alloys After Shot Peening, Oxidation and Hot Corrosion

In a prior companion study (Ref. 1), three different Ni-Cr coating compositions (29, 35.5, 45 wt% Cr) were applied at two thicknesses by Plasma Enhanced Magnetron Sputtering (PEMS) to two similar Ni-based disk alloys. One coating also received a thin ZrO2 overcoat. The low cycle fatigue (LCF) life of each coating was determined at 760 C and was less than that of the uncoated specimens. In this followon effort, shot peening was examined as a means to improve the as-deposited coating morphology as well as impart a residual compressive stress in the near-surface region. After evaluating the effect of the shot peening on the LCF life, the effectiveness of the shot-peened coating in protecting the disk alloy from oxidation and hot corrosion attack was evaluated. This evaluation was accomplished by exposing coated and shot-peened specimens to 500 h of oxidation followed by 50 h of hot corrosion, both at 760 C in air. These exposed specimens were then tested in fatigue and compared to similarly treated and exposed uncoated specimens. For all cases, shot peening improved the LCF life of the coated specimens. More specifically, the highest Cr coating showed the best LCF life of the coated specimens after shot peening, as well as after the environmental exposures. Characterization of the coatings after shot peening, oxidation, hot corrosion and LCF testing is presented and discussed

Variable Angle Locking Compression Plate as Alternative Fixation for Jones Fractures:: A Case Series

Introduction. Jones fractures pose many challenges for the treatingsurgeon and can cause significant disability for some patients. Theaim of this study was to review the results of using a variable anglelocking compression plate as an alternative fixation method in thetreatment of Jones fractures.Methods.xA retrospective chart review was conducted of patientswho had undergone fixation of Jones fracture with a variable anglelocking compression plate from September 2012 through February2016. Radiographs of the preoperative and six-week postoperativeand postoperative follow-up outcomes, including complication andhardware removal, were collected.Results. Twenty-three cases met the inclusion/exclusion criteria.The overall bony union rate was 96% at six-week postoperative and100% at 20-week postoperative. Mean age was 30 ± 16 years, andmean BMI was 30.7 ± 5.2 kg/m2. Three patients (13%) had plateremoval: two (9%) were due to irritation caused by shoe wearing andone patient (4%) had a skin infection (cellulitis) which was treatedwith intravenous antibiotics. One patient (4%) had developed deepvein thrombosis (DVT) that was resolved with anticoagulant withoutimplant removal. No fixation loss and no associated complicationsdeveloped from implant removal.Conclusions. Based on our limited experience, this study providedevidence that the variable angle locking compression plate may be analternative form of fixation for Jones fractures with a low complicationrate. This procedure seemed to provide a safe, reliable methodthat can achieve an anatomic reduction, stable fixation, rapid healing,and good results in the treatment of Jones fractures.Kans J Med 2019;12(2):28-32

Resonant optical control of the structural distortions that drive ultrafast demagnetization in Cr2_2O3_3

We study how the color and polarization of ultrashort pulses of visible light can be used to control the demagnetization processes of the antiferromagnetic insulator Cr$_2$O$_3$. We utilize time-resolved second harmonic generation (SHG) to probe how changes in the magnetic and structural state evolve in time. We show that, varying the pump photon-energy to excite either localized transitions within the Cr or charge transfer states, leads to markedly different dynamics. Through a full polarization analysis of the SHG signal, symmetry considerations and density functional theory calculations, we show that, in the non-equilibrium state, SHG is sensitive to {\em both} lattice displacements and changes to the magnetic order, which allows us to conclude that different excited states couple to phonon modes of different symmetries. Furthermore, the spin-scattering rate depends on the induced distortion, enabling us to control the timescale for the demagnetization process. Our results suggest that selective photoexcitation of antiferromagnetic insulators allows fast and efficient manipulation of their magnetic state.Comment: 7 pages, 5 figure

Time-Domain Separation of Optical Properties From Structural Transitions in Resonantly Bonded Materials

The extreme electro-optical contrast between crystalline and amorphous states in phase change materials is routinely exploited in optical data storage and future applications include universal memories, flexible displays, reconfigurable optical circuits, and logic devices. Optical contrast is believed to arise due to a change in crystallinity. Here we show that the connection between optical properties and structure can be broken. Using a unique combination of single-shot femtosecond electron diffraction and optical spectroscopy, we simultaneously follow the lattice dynamics and dielectric function in the phase change material Ge2Sb2Te5 during an irreversible state transformation. The dielectric function changes by 30% within 100 femtoseconds due to a rapid depletion of electrons from resonantly-bonded states. This occurs without perturbing the crystallinity of the lattice, which heats with a 2 ps time constant. The optical changes are an order-of-magnitude larger than those achievable with silicon and present new routes to manipulate light on an ultrafast timescale without structural changes