Miracle-dz/UniFAR-FTUs huggingface dataset:
Design of Curie point written magnetoresistance random access memory cells

Very high density magnetoresistance random access memory (MRAM) cells may be subject to thermal upset. This article describes designs that enhance thermal stability and increase ultimate density by using the combination of heat and magnetic field for writing data. The basic storage mechanism can be shape anisotropy, the coupling between an antiferromagnetic layer and a ferromagnetic layer, or a combination of the two. Two designs are described in this article. The first uses a low Curie point material with high shape anisotropy at room temperature. These cells use active semiconductor devices to restrict heating current to only one cell in an array. The second approach employs the interface coupling between a ferromagnetic film and an antiferromagnetic film as the storage mechansism. A cell may be written by heating above the Neel temperature and cooling the interface in a magnetic field by using orthogonal lines for heating and magnetic field. Heating and cooling times are a few nanoseconds. These design.
FAR-ULTRAVIOLET AND OPTICAL SPECTROSCOPY OF THE DETACHED WHITE DWARF-M DWARF BINARY RE J1629+780

We present optical and far ultraviolet observations, including IUE high and low dispersion spectroscopy of the (DA2+dM4-5) close binary, RE J1629+780, a very bright ROSAT EUV source. The optical data reveal emission reversals in the cores of the Balmer lines, which vary in strength but reveal no evidence of wavelength shifts reflecting orbital motion, suggesting that the red dwarf and the white dwarf are widely separated. Thus it is unlikely that irradiation plays a dominant role in the activity of the red dwarf. One dramatic increase in the intensity of the H-beta emission strength in the course of one hour indicates that the observed intensity variations are most likely related to flare activity on the red dwarf. Our analysis of Balmer and Lyman alpha features yield Teff = 42,500 ± 1300K and log g = 7.6 ± 0.3 for the DA2 white dwarf, which is consistent with the overall 900 A to 3200 A energy distribution derived from Voyager and IUE low dispersion spectra. Our analysis of three IUE echelle spectra reveal numerous lines of interstellar origin. Using a total of 13 ISM features we find a mean radial velocity of -13.57 ± 1.66 km/s for the interstellar features. However we found no evidence of trace metal absorbers levitated or accreited in the white dwarf photosphere nor any evidence of circumstellar or wind features. We estimate a lower limit hydrogen layer mass of 2.1 X 10-15 Msun for a stratified atmosphere based upon the non-detection of He II (1640). Tighter constraints on the helium abundance and the hydrogen layer mass, from EUV and X-ray data, are presented for both homogeneous and stratified atmospheric configurations.
Postcollapse hydrodynamics of SN 1987A : two-dimensional simulations of the early evolution

The first few seconds of the explosion of SN 1987A are modeled here using a 2D cylindrical geometry smooth particle hydrodynamics code. The success of the explosion is determined to be sensitive to the duration of the infall, the timing of the bounce, and the subsequent neutrino heating. A semianalytical model for the initial structure of the collapsed object is used to present two simulations that differ by the mass that has been allowed to collapse into a neutron star prior to the bounce. In the case of a short initial infall, the explosion fails due to excessive cooling. For a longer initial infall, the cooling is less and the explosion is successful although relatively weak. It is shown that in this case, a successful explosion is brought about by the presence of an entropy gradient which, combined with the gravitational pull of the neutron star, leads to extremely strong instabilities. The critical importance of the global circulation for the success of the explosion is demonstrated. 43 refs.
A study of two-dimensional flow past an oscillating cylinder

In this paper we describe a detailed study of the wake structures and flow dynamics associated with simulated two-dimensional flows past a circular cylinder that is either stationary or in simple harmonic cross-flow oscillation. Results are examined for Re=500 and a fixed motion amplitude of ymax/D=0.25. The study concentrates on a domain of oscillation frequencies near the natural shedding frequency of the fixed cylinder. In addition to the change in phase of vortex shedding with respect to cylinder motion observed in previous experimental studies, we note a central band of frequencies for which the wake exhibits long-time-scale relaxation oscillator behaviour. Time-periodic states with asymmetric wake structures and non-zero mean lift were also observed for oscillation frequencies near the lower edge of the relaxation oscillator band. In this regime we compute a number of bifurcations between different wake configurations and show that the flow state is not a unique function of the oscillation frequency. Results are interpreted using an analysis of vorticity generation and transport in the base region of the cylinder. We suggest that the dynamics of the change in phase of shedding arise from a competition between two different mechanisms of vorticity production.
Absence of runaways and divergent self-mass in nonrelativistic quantum electrodynamics

We derive the quantum-mechanical operator equation of motion for a point electron and show that (i) the electrostatic self-mass of a point electron is zero in quantum mechanics; (ii) the equation of motion does not admit runaway solutions; (iii) the correspondence limit of the solutions of the quantum-mechanical equation likewise does not display runaways; and (iv) the solutions do not violate the principle of causality in quantum mechanics.
Cosmic Rays, Nuclear Gamma Rays and the Origin of the Light Elements

The origin of cosmic rays has been a major mystery in astrophysics for nearly a century. However, any lingering doubt about whether the bulk of the cosmic rays (those with energies below about 1015 eV) are Galactic or extragalactic has been removed in the 1990s in favor of a Galactic origin. The question has been settled by gamma‐ray observations made by the Energetic Gamma Ray Experiment Telescope on the Compton Gamma Ray Observatory. The EGRET observations showed that the cosmic‐ray energy density in a nearby galaxy—the Small Magellanic Cloud—is much lower than that found locally in our own Galaxy and is thus inconsistent with a uniform extragalactic density. This discovery, of course, does not preclude an extragalactic origin for the very highest energy cosmic rays, which are observed above about 1019 eV. (See PHYSICS TODAY, January 1998, page 31). The power of about 1041 ergs/s required to maintain the cosmic rays throughout the Galaxy is most likely supplied by supernovae (figure 1). With a Galactic .
A post-editing approach to machine translation evaluation at the document-level

Machine translation has become ever more prominent in society with Google translate acknowledging over 500 million users in 2016. With this reliance on machine translation, it is important to determine quality and whether human parity has been reached. Automatic metrics like BLEU scores can be used to estimate the quality of machine translations but these methods are often considered unreliable. Therefore, manual evaluations campaigns are carried out including at the annual workshop on statistical machine translation (WMT). There has been an appeal in the machine translation community to start evaluating at the documentlevel to give annotators more context. As such, the direct assessment method used at WMT was adapted to suit a document-level evaluation instead of isolated sentences and segments. However, the method has fallen short at providing full document context while also failing to give annotators a chance to edit previous segments. The research undertaken aimed at addressing this problem of providing full document-level context while also ensuring high-levels of quality control for the crowd-sourced assessments. This project is the first to explore the use of post-editing at the document-level for machine translation with crowd-sourced annotations. The benefits of this approach over existing evaluation methodologies are that it gives full document context, removes subjective numerical judgements and it can specify where MT systems go wrong. Evaluations were carried out by researchers as well as crowd-sourced workers. In addition, inter-annotator agreements levels were calculated against these post-edits using Cohen’s kappa. The results demonstrated some correlation in terms of machine translation system rankings with official results that were obtained at WMT 20. In the crowd-sourced evaluation campaign, 2 cluster groups of rankings emerged compared to 4 cluster groups of rankings from official WMT results. In terms of inter-annotator agreement for post-editing, it was found that annotators showed moderate agreement when choosing to edit or not edit a segment (κ = 0.4821) but this agreement was not as strong when crowd-sourcing (κ = 0.2826). Furthermore, the QC mechanisms proved effective and allowed for a manual inspection of submitted data, something that current machine translation evaluations can not feasibly do. Overall, the work carried out demonstrated that crowd-sourcing document-level post-edits is a feasible approach to machine translation evaluation.
Proposed Methodology for Accuracy Improvement of LOD1 3D Building Models Created Based on Stereo Pléiades Satellite Imagery

Three-dimensional city models play an important role for a large number of applications in urban environments, and thus it is of high interest to create them automatically, accurately and in a cost-effective manner. This paper presents a new methodology for point cloud accuracy improvement to generate terrain topographic models and 3D building modeling with the Open Geospatial Consortium (OGC) CityGML standard, level of detail 1 (LOD1), using very high-resolution (VHR) satellite images. In that context, a number of steps are given attention (which are often (in the literature) not considered in detail), including the local geoid and the role of the digital terrain model (DTM) in the dense image matching process. The quality of the resulting models is analyzed thoroughly. For this objective, two stereo Pléiades 1 satellite images over Iasi city were acquired in September 2016, and 142 points were measured in situ by global navigation satellite system real-time kinematic positioning (GNSS-RTK) technology. First, the quasigeoid surface resulting from EGG2008 regional gravimetric model was corrected based on data from GNSS and leveling measurements using a four-parameter transformation, and the ellipsoidal heights of the 142 GNSS-RTK points were corrected based on the local quasigeoid surface. The DTM of the study area was created based on low-resolution airborne laser scanner (LR ALS) point clouds that have been filtered using the robust filter algorithm and a mask for buildings, and the ellipsoidal heights were also corrected with the local quasigeoid surface, resulting in a standard deviation of 37.3 cm for 50 levelling points and 28.1 cm for the 142 GNSS-RTK points. For the point cloud generation, two scenarios were considered: (1) no DTM and ground control points (GCPs) with uncorrected ellipsoidal heights resulting in an RMS difference (Z) for the 64 GCPs and 78 ChPs of 69.8 cm and (2) with LR ALS-DTM and GCPs with corrected ellipsoidal height values resulting in an RMS difference (Z) of 60.9 cm. The LOD1 models of 1550 buildings from the Iasi city center were created based on Pléiades-DSM point clouds (corrected and not corrected) and existing building sub-footprints, with four methods for the derivation of the building roof elevations, resulting in a standard deviation of 1.6 m against high-resolution (HR) ALS point cloud in the case of the best scenario. The proposed method for height extraction and reconstruction of the city structure performed the best compared with other studies on multiple satellite stereo imagery.
Model Reduction and Dynamic Aggregation of Grid-Forming Inverter Networks

This paper presents a model-order reduction and dynamic aggregation strategy for grid-forming inverter-based power networks. The reduced-order models preserve the network current dynamics as well as the action of the inverter current-reference limiter. Inverters based on droop, virtual synchronous machine, and dispatchable virtual oscillator control are considered, a generic model for all three control strategies is presented, and a smooth function approximation is utilized to represent the action of the current-reference limiter. The network is assumed to be composed of lines with homogeneous $l/r$ ratios. Given such a system, our approach involves three steps. First, time-domain Kron reduction is used to reduce the dimensions of the electrical network model. Next, dynamic aggregate models are developed for parallel-connected inverters. Finally, singular perturbation analysis is used to systematically eliminate fast-varying dynamics in both the network model and the grid-forming inverter single/aggregate models. Numerical simulation results benchmark the response of the reduced-order aggregate models against the full-order models from which they are derived, and we demonstrate significant savings in computation cost with limited loss of accuracy.
Extracting References from Political Speech Auto-Transcripts

This paper presents an unsupervised method for counting references in noisy auto-transcribed political speeches. Transcriptions are vectorized using learned embeddings which are then clustered using k -means resulting in groups of words which represent highly granular, specific topics within the text. Words from each cluster are then extracted from each transcript, counted, and arranged for time-series analysis. The approach finds semantically coherent topics representing specific references despite transcription inac-curacies. We use this framework to extract references from over 400 political speech transcriptions from a 2016 U.S. presidential campaign.
Understanding UI attacks on Android

In this thesis, we closely examine an important type of attack against Android smartphones that exploit weaknesses in the user interface. In particular, we study, analyze and implement the “Keystroke Inference #3” attack from the “Cloak and Dagger” paper by Fratantonio et al. [1, 2], which enables an attacker to steal sensitive input such as passwords. The attack takes advantage of a vulnerability that was subsequently patched on all newer Android versions. Yet, it still affects a significant user base that utilizes older devices. In this paper, we present the end-to-end attack implementation of the “Keystroke Inference #3” concept and elaborate on in-depth details. In order to make the attack feasible certain technical challenges needed to be solved, therefore our developed approaches are presented as well. After the evaluation of the results, we show that the implementation is applicable to a wide range of Android versions. We then present our novel defense technique OverlayShifter, which fully prevents the attack while being independent of operating system modifications. Moreover, characteristics that facilitate the detection of the attack are discussed.
Study on a piezoelectric structure based active vibration isolation system for high precision equipment

Vibration is one of the limiting factors to achieve ultra precision in ultra precision metrology or manufacturing equipments. In this paper, an active vibration isolation system using piezoelectric actuators for ultra precision equipment is presented. The effectiveness of the vibration suppression by piezoelectric actuators under different configurations is investigated numerically. The model reference adaptive control is taken for the control of piezoelectric actuator. The result of theoretical analysis and simulation demonstrate the performance and effectiveness of the system.
On modelling early life weight trajectories

There is broad recognition that early life growth trajectories can contribute to the study of the onset and development of several health outcomes. We review the random‐effects specifications of two models that have been purposely developed to describe anthropometric data and a shape invariant random‐effects model recently proposed in the statistical literature. They are compared in terms of their ability to extract salient and biologically meaningful features of growth in infancy and also to represent the data validly. We discuss advantages and limitations in choosing and interpreting each of the models by using longitudinal weight data taken from 0 to 4 years from three contemporary birth cohorts.
Transient growth in circular pipe flow. II. Nonlinear development

The Navier–Stokes equations for circular pipe flow are integrated using direct numerical simulation for the case of transitional Reynolds number. Previous work on linear disturbances (reported in Part I) is exploited for the simulation of low to moderate amplitude disturbances where it is found that the transient growth mechanism persists in the nonlinear development with the evolution attributable to the linear mechanism remaining of considerable significance. A hypothesis of Trefethen et al. [Science 261, 578 (1993)] concerning the role of nonlinearity in the transition process and ultimately in turbulence is elucidated and given support. It is suggested that nonlinearity is essential in continually perturbing the eigenmodes of the flow in such a way that each mode is never permitted to relax to its least stable eigenstate (damped in the subcritical case). In this way, the linear growth mechanism can be regarded as an underpinning component of the general nonlinear feedback insofar as it is the only part which can extract energy from the mean flow and thus yield a net increase in disturbance energy. The physical aspects of the flow simulations are consistent with puff formation where, using a pair of helical waves as initial data, a sharp trailing front is formed naturally; axisymmetric ring vortices are generated and the general flow characteristics are in broad agreement with experiment.
Supernovae and Dark Energy

Type Ia supernovae provide a precise luminosity distance at redshift as high as z 2. At present nearly 200 SN Ia paint a consistent picture that ΩA - 1. 4ΩM = 0.35 ± 0.14 (if w = -1). If ΩT = 1, SN Ia tell us ΩM = 0.28 ± 0.05, independent of any other measurements. Adopting a prior based on the 2dF redshift survey constraint on ΩM and assuming a flat universe, then -1.48 -1, we obtain w < -0.73 at 95% confidence. Understanding systematic errors is of paramount importance, both because they may affect our present results and they will limit the eventual precision achievable. Possible sources of error include photometric error, dust extinction, evolution of SN Ia selection effects, K-corrections, and gravitational lensing, all which could vary with redshift. There are many efforts underway to push to higher redshift and to control possible observational systematic errors the bottom line is that the acceleration reported earlier appears to be confirmed. The propagation of systematic error in luminosity distance to inferred w or w(z) depends critically on how much is known about ΩM. For example, at fixed ΩM a systematic uncertainty in dlum of 0.04 mag corresponds to a 10% uncertainty in w, but this becomes much worse if ΩM is not known. We will have some good constraints on ΩM, either directly from 2dF or SDSS, or indirectly from WMAP whose constraints in the (ΩM, w) plane run more or less perpendicular to the SN Ia (but they can also have systematic errors themselves). Theoretical models for SN Ia are now able to make multi-wavelength light curves and spectra which are a decent match to observation. The luminosity-decline rate correlation depends primarily on the amount of 56Ni produced in the explosion. There are other, more subtle effects which are also being elucidated, for example, increasing initial metallicity (in the form of neutron-rich 56Fe and 22Fe) diminishes the neutron-poor 56Ni and dims the explosion. Unfortunately we have very little idea at present about what causes a WD to explode. A small fraction of WD explode, and those that do wait a long time between their formation and their explosion. Without initial conditions, there is a lot of room for systematic error at the 0.02 mag level from SN Ia explosions, and whether they depend in a serious way with z and therefore limit our ability to measure w(z) remains to be seen. It may be that we can measure dlum(z) to 1% (0.02 mag) by controlling only observational systematics, or it may be that we incur significant systematic errors for which we do not have the requisite information to realize their presence or correct for them.
PHASE COHERENCE OF 2D EXCITONS IN GaAs-AlGaAs QUANTUM WELLS

We have studied photon echoes on a picosecond timescale from 2D excitons in GaAs-AlGaAs quantum wells. A theoretical model is used which considers phase relaxation during excitation. We find considerable deviations from the usual photon echo behavior for pulse lengths comparable to the phase coherence time. Line shape analyses of our experimental data yield the phase coherence times which are found to vary strongly across the inhomogeneously broadened exciton line.
Effects of prior antiplatelet use on futile reperfusion in patients with acute ischemic stroke receiving endovascular treatment

Introduction: We evaluated the effects of prior antiplatelet use (APU) on futile reperfusion (FR) after endovascular treatment (EVT) in acute ischemic stroke. Material and methods: We consecutively collected data of 9369 patients with acute ischemic stroke from four university-affiliated multicenter registry databases over 92 months. We enrolled 528 patients with acute stroke receiving EVT. Among them, we defined FR in subjects as a 3-month modified Rankin Scale score of >2 despite successful reperfusion after EVT. We classified patients into two groups: prior APU and no prior APU. We used propensity score matching (PSM) to overcome the imbalance in multiple covariates between the two groups. After PSM, we compared the baseline characteristics between the two groups and performed multivariate analysis to determine whether prior APU affected FR and other stroke outcomes. Results: The overall FR rate in the present study was 54.2%. In the PSM cohort, the FR was lower in the prior APU group than that in the no prior APU group (66.2% vs 41.5%, p < 0.001). In the multivariate analysis using the PSM cohort, prior APU significantly reduced the risk of FR (odds ratio (OR), 0.32; 95% confidence interval (CI), 0.18–0.55; p = 0.001) and stroke progression (OR, 0.38; 95% CI, 0.15–0.93; p = 0.03). Prior APU was not associated with symptomatic hemorrhagic transformation in this study. Conclusion: Prior APU potentially reduced FR and stroke progression. Further, prior APU was not associated with symptomatic hemorrhagic transformation in patients receiving EVT. APU pretreatment can be a modifiable predictor of FR in clinical practice.