Miracle-dz/UniFAR-FTUs huggingface dataset:
(Pt/Co/Pt)/X multilayer films with high Kerr rotations and large perpendicular magnetic anisotropies

We have sputter‐deposited a series of (Pt/Co/Pt)/X multilayer structures with X=Pd,Ag,Cu displaying large Kerr rotations with improved perpendicular anisotropy and magnetic coercivity compared to the corresponding Co/X multilayers. In particular, Ar‐sputtered (Pt/Co/Pt)/Pd multilayers, with the Pt layer thicknesses corresponding to one atomic monolayer, present Kerr rotations of the order of 0.26°, perpendicular anisotropy energies of 33×106 ergs/cc (Co) or better, and magnetic coercivities as high as 8 kOe.
The study of an iterative method for the reconstruction of images corrupted by Poisson and Gaussian noise

In 1993, Snyder et al investigated the maximum-likelihood (ML) approach to the deconvolution of images acquired by a charge-coupled-device camera and proved that the iterative method proposed by Llacer and Nuñez in 1990 can be derived from the expectation-maximization method of Dempster et al for the solution of ML problems. The utility of the approach was shown on the reconstruction of images of the Hubble space Telescope. This problem deserves further investigation because it can be important in the deconvolution of images of faint objects provided by next-generation ground-based telescopes that will be characterized by large collecting areas and advanced adaptive optics. In this paper, we first prove the existence of solutions of the ML problem by investigating the properties of the negative log of the likelihood function. Next, we show that the iterative method proposed by the above-mentioned authors is a scaled gradient method for the constrained minimization of this function in the closed and convex cone of the non-negative vectors and that, if it is convergent, the limit is a solution of the constrained ML problem. Moreover, by looking for the asymptotic behavior in the regime of high numbers of photons, we find an approximation that, as proved by numerical experiments, works well for any number of photons, thus providing an efficient implementation of the algorithm. In the case of image deconvolution, we also extend the method to take into account boundary effects and multiple images of the same object. The approximation proposed in this paper is tested on a few numerical examples.
A new method for evaluating singular integrals in stress analysis of solids by the direct boundary element method

The purpose of this paper is to report on a new and efficient method for the evaluation of singular integrals in stress analysis of elastic and elasto-plastic solids, respectively, by the direct boundary element method (BEM). Triangle polar co-ordinates are used to reduce the order of singularity of the boundary integrals by one degree and to carry out the integration over mappings of the boundary elements onto plane squares. The method was subsequently extended to the cubature of singular integrals over three-dimensional internal cells as occur in applications of the BEM to three-dimensional elasto-plasticity. For this purpose so-called tetrahedron polar co-ordinates were introduced. Singular boundary integrals stretching over either linear, triangular, or quadratic quadilateral, isoparametric boundry elements and singular volume integrals extending over either linear, tetrahedral, or quadratic, hexahedral, isoparametric internal cells are treated. In case of higher order isoparametric boundary elements and internal cells, division into a number of subelements and subcells, respectively, is necessary. The analytical investigation is followed by a numerical study restricted to the use of quadratic, quadrilateral, isoparametric boundary elements. This is justified by the fact that such elements, as opposed to linear elements, yield singular boundary integrals which cannot be integrated analytically. The results of the numerical investigation demonstrate the potential of the developed concept.
Evolution of ultrasound beamformers

Real-time ultrasonic imaging systems have been available for more than thirty years. During this time much has occurred to the basic architecture and functions of these clinical systems and their beamformers, which are, in many ways, the most important components of these systems. This talk will review some of the changes that have occurred and will discuss current trends in beamformer design. Throughout most of the 30 years of real time imaging, analog beamformers have been the mainstay of all instruments. The common methods for the implementation of analog beamformers for annular, linear/curved arrays, and phased arrays will be reviewed and the distinguishing characteristics identified. At the present time the industry is undergoing a major shift toward digital beamformation with the introduction of several commercial systems. Given that the earliest digital systems were available roughly 15 years ago, it is fair to say that the introduction of digital beamformers has been relatively slow. Today this shift seems to be gaining momentum. Some of the factors causing these shifts will be reviewed along the the common types of designs and implementations. The ongoing search for improved imaging performance will continue to introduce new challenges for beamformer designers. Among already proposed imaging methods and techniques are elevation focusing (1.5D arrays), synthetic apertures, 2D and sparse arrays, phase aberration correction, and others. The most common complication introduced by these is a significant increase in channel count. Further, there will also be beamformer design issues related to signal processing. These include not only Doppler processing but also the processing of signals due to novel contrast agents. Finally, with advances in computer and microelectronics technologies, the way we view beamformation may have to undergo sizeable changes. These topics will be reviewed not only as technical challenges but also in light of the constraints introduced by today's marketplace.
THE SPIRE INSTRUMENT FOR HERSCHEL

SPIRE, the Spectral and Photometric Imaging Receiver, will be a bolometer instrument for ESA’s Herschel satellite. Its main scientific goals are deep extragalactic and galactic imaging surveys and spectroscopy of star-forming regions in own and nearby galaxies. The SPIRE detectors are feedhorn-coupled NTD “spider-web” bolometers. The instrument comprises a three-band imaging photometer covering the 250-500 µm range, and an imaging Fourier Transform Spectrometer (FTS) covering 200-670 µm. The photometer has a field of view of 4 x 8 arcminutes which is observed simultaneously at 250, 350 and 500 µm, with dichroic beam dividers separating the three spectral bands. Its angular resolution is determined by the telescope diffraction limit, with FWHM beam widths of approximately 17, 24 and 35 arcseconds at 250, 350 and 500 µm, respectively. An internal beam steering mirror can be used for spatial modulation of the telescope beam, and observations can also be made by scanning the telescope without chopping, providing better sensitivity for source confusion-limited deep surveys. The FTS has a field of view of 2.6 arcminutes and an adjustable spectral resolution of 0.04 - 2 cm �1 (λ/∆λ = 20 - 1000 at 250 µm). It
A Simple Model for the Interaction between Vertical Eddy Heat Fluxes and Static Stability

Abstract A model designed for studying the interaction between vertical eddy beat fluxes and the vertical temperature structure in midlatitudes is presented. A temperature profile is obtained for the model by computing an equilibrium among heating rates from simplified representations of the large-scale vertical eddy heat flux, moist convection and radiation. In particular, the eddy flux profile is obtained from the quasi-geostrophic, linear baroclinic instability of a single wave, and the eddy amplitude is either specified or else obtained from a closure assumption. Tests using a variety of input conditions indicate that the most appropriate single wave to use is the most unstable mode of the instability problem. The model's temperature and Brunt-Vaisala frequency profiles am compared with observed profiles. The most unstable mode computations, in particular, reproduce well the observed profiles for both winter and summer conditions. Model runs with various eddy amplitudes show that particular aspects of.
Pressure-induced phase transitions and structure of chemically ordered nanoregions in the lead-free relaxor ferroelectric Na_{1/2}Bi_{1/2}TiO_{3}

We investigate the phase stability of Na1/2Bi1/2TiO3, a prototype lead-free relaxor material, under pressure. By means of total energy calculations within density functional theory, we study the pressure stability of several structures with polar and antipolar distortions, in-phase and out-of-phase tilts, and different chemically ordered configurations. Under positive (compressive) pressure an orthorhombic Pbnm-like phase is stabilized above 3 GPa. At negative (tensile) pressure a non-tilted polar P4mm-like phase is stable. At zero pressure two phases are coexisting. The local chemical configuration determines whether the high-pressure Pbnm-like or another tilted and polar R3c-like structure is favored. Thus, two different variants of pressure phase diagrams depending on the cation arrangement are obtained, which raises the question of the existence of a mixed phase ground state in the disordered system. We discuss the stability of the mixed phase state in terms of lattice and tilt misfits and possible shapes and ferroic properties of the coexisting regions with different average structures. Our results clearly support the view that there are chemically ordered nanoregions with their own local ferroic properties embedded in a chemically disordered ferroelectric matrix representing the ground state.
Visualization of short surface acoustic waves by stroboscopic x-ray topography: analysis of contrast

In this paper the capabilities of stroboscopic x-ray topography to visualize the propagation of short (<10 μm) surface acoustic waves (SAW) in single crystals are analysed. Experiments with LiNbO3 crystals under SAW excitation were carried out at the ID19 beam line of the European synchrotron radiation facility. The developed theoretical analysis of the SAW-induced contrast in Bragg scattering geometry helped to optimize experimental conditions and receive high quality images with well-resolved individual acoustic wave fronts. The basic contrast mechanism is related to the SAW-induced corrugation of atomic planes that causes the focusing of x-rays. The focal distance is directly proportional to the SAW wavelength and inversely proportional to the deformation amplitude at the crystal surface. Simulations of diffraction contrast allowed us to conclude that the best contrast is achieved when the acoustic wave vector is perpendicular to the x-ray scattering plane and the sample/film distance equals 2–4 focal distances.
Polarization Variability among Wolf-Rayet Stars. VII. The Single Stars WR 14, WR 25, and WR 69

We have monitored over an interval of 1 month the linear polarization in visible light of three single Wolf-Rayet stars, WR 14 (WC6), WR 25 (WN7), and WR 69 (WC9). As for other early-type WC stars, WR 14 is not significantly variable (at the σ∼0.03% level) during this set of observations; however, its mean polarization level is significantly different from its value in 1987. The two other stars do vary (σ∼0.06%) as expected for late-type W-R stars of either sequence
Short-term hydro-thermal coordination by Lagrangian relaxation: solution of the dual problem

This paper addresses the short-term hydrothermal coordination problem. This problem is large-scale, combinatorial and nonlinear. It is usually solved using a Lagrangian relaxation approach. In the framework of the Lagrangian relaxation, this paper provides a novel, nonoscillating and efficient multiplier updating procedure. This procedure advantageously compares with previously reported procedures such us subgradient and bundle methods. A realistic large-scale case study is used to illustrate the behavior of the proposed procedure.
The Computation of the Electric Field Quantities in SAW Devices

P.O. Box 5031, A computational technique to determine the electric properties of a SAN device in integrated circuits, where the electric quantities are independent of the acoustic quantities, is presented. The problem is reduced to a dual boundary problem, which is solved by a new iterative method employing the minimization of the integrated square error. The relation between spatial and spectral quantities of the dual boundary value problem is performed numerically using the Fast Fourier Transform. The efficiency of the proposed method is discussed.
Variable-Structure Systems from Graphs and Grammars

Variable-structure systems are those for which the available objects and their relationships can enter or leave the problem as a function of time or depending on the values of other variables. We seek to define probabilistic generative models for variable-structure systems in sufficient generality for use in complex scientific and pattern recognition applications. We define a semantic map, Y, by which model specifications map to model semantics for variable-structure systems. The specification takes the form of (a) a labelled graph or “dependency diagram” (some of whose nodes are labelled with random variables), or (b) a context-sensive stochastic parameterized grammar (SPG), a particular kind of “dynamical grammar”. The semantics takes the form of a joint probability density function (pdf), in the case of a graph, or an infinite-dimensional time evolution operator on joint probability density functions for a dynamical grammar. We illustrate these frameworks by treating, with dependency diagrams and dynamical grammars, an elementary example: context-free but resource-bounded trees of conditionally dependent feature vectors. This model can serve as a scaffold for many other variable-structure systems. Fixed-structure Dependency Diagram (DD) classes include graphical models such as Markov Random Fields, Bayes Nets, and Factor Graphs, as well as Constraint Networks. By adding new kinds of node and link labels to the graph specification we can extend such DD classes to efficiently represent variable-structure systems and other highly structured probabilistic architectures, with a formal semantics. The DD notation extensions proposed here include: interaction-gating links (for conditional links and nodes); index nodes and links (with and without weight sharing for structured architectures) that generalize “Plates” with multiple levels of indexing and controllable scope; undirected constraint links; and derived types such as node existence and time delay links. Diagrams for the feature tree model illustrate the differences in principle between dependency diagrams for fixed and variable-structure systems. For SPG’s we relate the probability distributions on continuous-time and discrete-time execution results for such grammars, and show how they express resource-limited feature trees. We show how perturbation theory gives rise to an approach both to analysing and to simulating continuous-time executions of dynamical grammars. Finally we discuss the relationships between DD and SPG frameworks, including their synergistic use in multiscale modeling.
Specific heat of bismuth at liquid helium temperatures

The specific heat of bismuth has been investigated in the liquid helium region down to 1.3°K by means of a new vacuum calorimeter. The Debye θ is found to increase from 103.5 to 120 in the range 4.1 to 2°K and appears to attain a constant value at lower temperatures. Evidence is obtained for an electronic contribution of 0.114×10 -4 T calories/°K to the atomic heat of bismuth.
Measurement of radiative properties of ash and slag by FT-IR emission and reflection spectroscopy

This article presents laboratory measurements of the radiative properties of ash and slag deposits that have been extracted from combustion devices. The measurements were made by a technique employing a sample heating device that is coupled to a Fourier Transform Infrared (FT-IR) spectrometer to measure the sample's emission and directional-hemispherical reflection. By this technique, the temperature at the measurement point and the spectral emittance of the surface are both obtained. The measurements are then related to the physical and chemical properties of the surface to determine what controls the radiative properties. The measurements have shown that the physical state of a deposit (i.e., fused, sintered, or packed particles) greatly influenced the measured spectral emittance. The results were in agreement with mathematical models that account for the physical properties.
Method for holographic femtosecond laser parallel processing using digital blazed grating and the divergent spherical wave

Abstract. A method for holographic femtosecond laser parallel processing is proposed, which can suppress the interference of zero-order light effectively and improve the energy utilization rate. In order to blaze the target pattern to the peak position of zero-order interference, a phase-only hologram containing a digital blazed grating is designed and generated, and the energy of the target pattern can be increased by 3.793 times in theory. In addition, by subsequently increasing the phase of the divergent spherical wave, the focal plane of the target pattern and the plane of the multiorder diffraction beam resulting from the pixelated structure of the spatial light modulator (SLM) can be separated. Both a high-pass filter and aperture are used to simultaneously eliminate the influences of zero-order light and multiorder interferential patterns. A system based on the phase-only SLM (with resolution of 1920×1080) is set up to validate the proposed method. The experimental results indicate that the proposed method can achieve high-quality holographic femtosecond laser parallel processing with a significantly improved energy utilization rate.
Hydrodynamics of accretion discs of variable thickness

We present a new model for the hydrodynamics of thin accretion discs. In the (r, φ ) plane full hydrodynamics is taken into account, while the time evolution of the disc thickness H is followed by assuming uniform expansion and contraction in the vertical direction. This amounts to a `one-zone' approximation for the vertical equation of motion. We show that the model correctly incorporates the fundamental mode of vertical oscillation of a disc for waves long compared with the disc thickness. A numerical scheme to solve these equations on an Eulerian grid is introduced and tested for validity. As an application we compute the excitation of disc thickness oscillations by the tidal field of a companion. Strong excitation occurs at the 2{:}1 resonance, at r ≃ 0.32 a, where a is the binary separation.
Cylindrical shock and detonation waves in magnetogasdynamics

Self-similar flow patterns are studied which arise when a cylindrically symmetric strong shock or detonation wave propagates outwards into a gas at rest in which the ambient density varies as the inverse square of the distance from the axis of symmetry along which flows a line current of either zero or finite constant strength. The electrical conductivity of the gas on either side of the wave is supposed perfect and the discontinuities discussed are either gasdynamic or magnetogas-dynamic in nature. It is shown that self-similar solutions exist for piston driven gasdynamic detonation and shock waves. Whilst no self-similar solutions may occur for magnetogasdynamic detonation waves, it is demonstrated that magnetogasdynamic shock waves do possess such solutions for which detailed flow patterns are presented.
Chromospheric reversals in the emergence of an ephemeral region

Context. The behaviour of both ephemeral regions and moving magnetic features has been often described for the photospheric layer, but not for the chromosphere. Both magnetic structures are related to the decay of active regions, but their actual role is not yet clear. Aims. Our aim is to observe and understand the behaviour of these structures in the chromosphere. Methods. We performed simultaneous photospheric and chromospheric spectropolarimetric observations of an ephemeral region and a moving magnetic feature. A new code developed for the reduction of spectropolarimetric data of several wavelengths observed simultaneously was used here for the first time and will be described here for future reference. The resulting Stokes profiles are analysed in detail. Results. The Stokes V profiles of Fe i 6301 and 6302 A are reversed in polarity with respect to the chromospheric Ca ii 8498 and 8542 A in the cases shown. They reveal a reversed magnetic field topology between these layers for both structures. The time evolution of the ephemeral region results in a cancellation of the chromospheric signal, while the ratio of Stokes V amplitudes of Fe i 6301 and 6302 A simultaneously informs us of a strengthening of the photospheric field. A scenario of the evolution of the ephemeral region is consequently suggested. Conclusions. The moving magnetic feature reveals itself as an exclusively photospheric feature, similar to the ephemeral region in the initial stages of its emergence. As the loop emerges into the chromosphere it is slowed down and does not reach the corona. Most probably, the opposite polarity background in the chromosphere prevents ascent into corona.
Fast projection algorithm for voxel arrays with object dependent boundaries

One-pass list-mode EM (OPL-EM), previously named ROPLE, is a new list-mode iterative reconstruction algorithm for high resolution, high count-rate and large field of view (FOV) PET scanners. The list-mode EM algorithm requires projecting every list-mode event from and into a large FOV with a large number of sub-millimeter voxels, and so substantial computing time is spent on back-projection and forward-projection operations. This paper presents an improved ray-tracing method, which extends the previously used projection algorithm, known as the Siddon algorithm, for a FOV with an irregularly bounded set of voxels instead of the traditional cubic array. This method can remove redundant projection operations in regions where no activity is present. This leads to typically a factor of 5 speed up compared to the conventional Siddon algorithm, and up to a factor of 2 speed up compared to the incremental approach.
Linear Depolarization Ratios of Columnar Ice Crystals in a Deep Precipitating System over the Arctic Observed by Zenith-Pointing Ka-Band Doppler Radar

AbstractThis study demonstrates that linear depolarization ratio (LDR) values obtained from zenith-pointing Ka-band radar Doppler velocity spectra are sufficient for detecting columnar ice crystals. During a deep precipitating system over the Arctic on 7 December 2013, the radar recorded LDR values up to −15 dB at temperatures corresponding to the columnar ice crystal growth regime. These LDR values were also consistent with scattering calculations for columnar ice crystals. Enhancements in LDR were suppressed within precipitation fallstreaks because the enhanced LDR values of columnar ice crystals were masked by the returns from the particles within the fallstreaks. However, Doppler velocity spectra of LDR within the fallstreak distinguished populations of slower-falling particles with high LDR (>−15 dB) and faster-falling particles with much lower LDR, suggesting that columnar ice crystals with high LDR coexisted with larger isometric particles that produced low LDR while dominating the total copolar re.