Miracle-dz/UniFAR-FTUs huggingface dataset:
Finite element models for thermal stress, axial tension, bending, and transversal compression of filamentary Bi-2223 tapes

Most filamentary superconductors have soft matrix metal and brittle filaments, which make them very vulnerable during mechanical loading. Therefore, estimating the impacts of loading in the conductors is important in designing applications. Finite element models provide a way to study the stress and strain distributions in a tape, taking into account the details of the tape cross section. This paper presents finite element models for some basic loading conditions met, for example, in magnets. The cases investigated include thermal stresses, axial tension, transversal compression, and bending of a tape. The focus is on Bi-2223 tapes, although similar models could also be applied to other conductor types. To evaluate the validity of the models, the results are compared to experimental data. The results of the models showed the same trends as the experiments, but some inaccurately known properties of the modelled tapes caused uncertainty in the models. For example, the stiffness and fracture strength of the filament material are essential parameters to pay attention to when the initiation of critical current is predicted.
Corrections to “Quench Property of Twisted-Pair MgB 2 Superconducting Cables in Helium Gas”

In Sec. II-B of the above-named work [ibid, vol. 25, no. 3, Jun. 2015, Art. ID 6200105], the last sentence should read as follows: "Voltage taps VS84 and VS85 are those at the top and bottom of strand #44. "
Role Of Adaptive Operators In Image Understanding

A system that hopes to accomplish robust automatic Image Understanding (IU) clearly needs techniques which can reason about what it is seeing and what it is trying to see. One need for reasoning is found in the ubiquitous operator parameter problem: the problem of setting parameters for low-level image computations. This paper explores this problem in the context of a complete IU system and presents an approach by which parameters are tuned with respect to high level features. Adaptive Operators accomplish this tuning by using 1) evaluations derived from specific object level features that rate the "goodness" of a segmented region; and 2) search methods which adaptively search for segmentation parameters producing the best region according to the evaluation. Adaptive Operators represent reasoning which ties together both the high-level, generally a-priori knowledge of an IU system and the lowest, purely computational level. Examples of Adaptive Operators and their performance are given in the context of a system to recognize buildings in aerial photographs.
Dwarf Cosmology with the Stromlo Missing Satellites Survey

The standard Lambda Cold Dark Matter model is considered to be a triumph of theoretical astrophysics but observations of the Milky Way and its system of satellite galaxies irresistibly signal that theory is incomplete on galactic and subgalactic scales. The Stromlo Missing Satellites (SMS) Survey is a critical endeavor to investigate at what level predictions of CDM cosmology are consistent with the observed matter distribution in the Milky Way halo. It will be the deepest, most extended search for optically elusive satellite galaxies to date, covering 20 000 square degrees of sky. The international SMS Survey collaboration will exploit 150 TB of CCD images in six filters acquired by the new SkyMapper telescope of the Australian National University over the next five years, expecting on completion photometric limits 0.5–1.0 mag fainter than the Sloan Digital Sky Survey. The primary objective of the program is to characterise the baryonic and dark matter components of a complete sample of MW satellites in the Southern hemisphere to provide stringent observational constraints for improving our understanding of how the Milky Way formed and what physical processes governed galaxy formation and evolution in general.
Amplification of three-dimensional perturbations during parallel vortex–cylinder interaction

A computational study has been performed to examine the amplification of three-dimensional flow features as a vortex with small-amplitude helical perturbations impinges on a circular cylinder whose axis is parallel to the nominal vortex axis. For sufficiently weak vortices with sufficiently small core radius in an inviscid flow, three-dimensional perturbations on the vortex core are indefinitely amplified as the vortex wraps around the cylinder front surface. The paper focuses on the effect of viscosity in regulating amplification of three-dimensional disturbances and on assessing the ability of two-dimensional computations to accurately model parallel vortex–cylinder interaction problems. The computations are performed using a multi-block structured finite-volume method for an incompressible flow, with periodic boundary conditions along the cylinder axis. Growth of three-dimensional flow features is examined using a proper-orthogonal decomposition of the Fourier-transformed vorticity field in the azimuthal and axial directions. The interaction is examined for different axial wavelengths and amplitudes of the initial helical vortex waves and for three different Reynolds numbers.
Reverberant acoustic energy in auditoria that comprise systems of coupled rooms

A frequency-dependent model for reverberant energy in coupled rooms is developed and compared with measurements for a 1:10 scale model and for Bass Hall, Ft. Worth, TX. At high frequencies, prior statistical-acoustics models are improved by geometrical-acoustics corrections for decay within sub-rooms and for energy transfer between sub-rooms. Comparisons of computational geometrical acoustics predictions based on beam-axis tracing with scale model measurements indicate errors resulting from tail-correction assuming constant quadratic growth of reflection density. Using ray tracing in the late part corrects this error. For mid-frequencies, the models are modified to account for wave effects at coupling apertures by including power transmission coefficients. Similarly, statical-acoustics models are improved through more accurate estimates of power transmission measurements. Scale model measurements are in accord with the predicted behavior. The edge-diffraction model is adapted to study transmission through.
Matrix-isolated Nano-sized Carbon Grains as an Analog for the 217.5 Nanometer Feature Carrier

The effect of particle shape or particle clustering on the extinction behavior of nano-sized hydrogenated carbon grains is investigated experimentally. The particles were extracted by a molecular beam technique at different condensation and clustering states and isolated in an argon matrix for UV spectroscopy. The state of clustering in the samples was controlled by transmission electron microscopy analysis. The simple spherical morphology of the matrix-isolated nonagglomerated particles permitted the derivation of reliable optical constants. A clear correlation was found between the measured UV feature width and the degree of particle clustering, in agreement with theoretical investigations based on the derived optical data. Therefore, the results prove unambiguously the expectation that the optical properties of carbonaceous grain material are strongly influenced by the particle shape and the clustering degree. For particles produced in hydrogen-containing atmospheres, the UV extinction peak was shifted blueward to a position close to the 217.5 nm hump. This shift was found to be nearly independent of the amount of hydrogen in the condensation zone. We also discuss the infrared spectra of the hydrogenated carbon materials. The astrophysical implications of the results are discussed with regard to the observational as well as the elemental abundance constraints.
Evidence for strong secondary electron emission in the tokamak scrape-off layer

A novel method to measure net secondary electron emission yield due to primary electron irradiation from a tokamak scrape-off layer plasma is described. High emission coefficients close to unity are obtained independent of the electron temperature. Enhanced elastic backscattering of low-energy primary electrons, already identified as an important phenomenon in many other fields of research, is likely to explain the high yields.
An X‐FEM approach for large sliding contact along discontinuities

The extended finite element method (X‐FEM) has been developed to minimize requirements on the mesh design in a problem with a displacement discontinuity. This advantage, however, still remains limited to the small deformation hypothesis when considering sliding discontinuities. The approach presented in this paper proposes to couple X‐FEM with a Lagrangian large sliding frictionless contact algorithm. A new hybrid X‐FEM contact element was developed with a contact search algorithm allowing for an update of contacting surfaces pairing. The stability of the contact formulation is ensured by an algorithm for fulfilling Ladyzhenskaya‐Babuska‐Brezzi (LBB) condition. Several 2D simple examples are presented in this paper in order to prove its efficiency and stability. Copyright © 2008 John Wiley & Sons, Ltd.
The source of magnetic fields in (neutron-) stars

Abstract Some arguments, none entirely conclusive, are reviewed about the origin of magnetic fields in neutron stars, with emphasis of processes during and following core collapse in supernovae. Possible origins of the magnetic fields of neutron stars include inheritance from the main sequence progenitor and dynamo action at some stage of evolution of progenitor. Inheritance is not sufficient to explain the fields of magnetars. Energetic considerations point to differential rotation in the final stages of core collapse process as the most likely source of field generation, at least for magnetars. A runaway phase of exponential growth is needed to achieve sufficient field amplification during relevant phase of core collapse; it can probably be provided by a some form of magnetorotational instability. Once formed in core collapse, the field is in danger of decaying again by magnetic instabilities. The evolution of a magnetic field in a newly formed neutron star is discussed, with emphasis on the existence of stable equilibrium configurations as end products of this evolution, and the role of magnetic helicity in their existence. A particularly puzzling problem is the large range of field strengths observed in neutron stars (as well as in A stars and white dwarfs). It implies that a single, deterministic process is insufficient to explain the origin of the magnetic fields in these stars.
A Non-Interior-Point Continuation Method for Linear Complementarity Problems

This paper presents a continuation method for linear complementarily problems based on a new smooth equation formulation. In particular, the case of a linear complementarity problem defined by a positive semidefinite or $P_0 $ matrix is studied in detail. Extensive numerical testing of the continuation method is performed for both problems in the literature and randomly generated problems.
Categorical Rhythm Perception as a Result of Unilateral Assimilation in Time-Shrinking

In previous studies, we established an illusion of time perception that we called time-shrinking: an empty time interval, immediately preceded by a slightly shorter time interval, is underestimated. In the first experiment of the present study, we examined the perceived duration not only of the second interval (t2), but also of the first interval (tl). The empty time intervals tl and t2, making a total duration of 90,180, 360, or 720 ms, were presented such that the time ratio between them changed systematically. The points of subjective equality of tl and t2 were established by the method of adjustment. In the patterns typically susceptible to timeshrinking, that is, in which t2 was underestimated, tl was perceived almost vertically. In the second experiment, listeners had to bisect an empty duration of 180 ms, marked by sound bursts. The bisecting sound marker was positioned closer to the initial marker than to the final one. Thus, tl had to be shorter than t2 in order for a regular pattern to be perceived. In the third experiment, just-noticeable forward and backward displacements of the middle sound marker were measured by a transformed updown method. The prediction that the interval of uncertainty was closer to the initial than to the final sound marker was confirmed. The three experiments demonstrated the existence of unilateral temporal assimilation, and it is argued that this perceptual mechanism causes a category of 1:1 rhythms, despite a considerable change in temporal ratio between two contiguous time intervals.
Slit height corrections in small angle X-ray scattering

A method of correcting experimental small angle x-ray scattering curves for the effects of the height of the collimating slits is developed. The method has the advantage of eliminating the need for numerical differentiation of the experimental curve. An expression suitable for numerical calculation is given, and an analysis is made of the error in the numerical approximation. The results of some applications of these slit correction techniques are discussed. (auth)
Clinical severity prediction of COVID-19 admitted patients in Spain: SEMI and REDISSEC cohorts

This report addresses, from a machine learning perspective, a multi-class classification problem to predict the first deterioration level of a COVID-19 positive patient at the time of hospital admission. Socio-demographic features, laboratory tests and other measures are taken into account to learn the models. Our output is divided into 4 categories ranging from healthy patients, followed by patients requiring some form of ventilation (divided in 2 categories) and finally patients expected to die. The study is conducted thanks to data provided by "Sociedad Espanola de Medicina Interna" (SEMI) and "Red de Investigacion en Servicios de Salud de Enfermedades Cronicas" (REDISSEC). Results show that logistic regression is the best method for identifying patients with clinical deterioration.
Forecasting influenza incidence as an ordinal variable using machine learning

Many mechanisms contribute to the variation in the incidence of influenza disease, such as strain evolution, the waning of immunity and changes in social mixing. Although machine learning methods have been developed for forecasting, these methods are used less commonly in influenza forecasts than statistical and mechanistic models. In this study, we applied a relatively new machine learning method, Extreme Gradient Boosting (XGBoost), to ordinal country-level influenza disease data. We developed a machine learning forecasting framework by adopting the XGBoost algorithm and training it with surveillance data for over 30 countries between 2010 and 2018 from the World Health Organisation's FluID platform. We then used the model to predict incidence 1- to 4-week ahead. We evaluated the performance of XGBoost forecast models by comparing them with a null model and a historical average model using mean-zero error (MZE) and macro-averaged mean absolute error (mMAE). The XGBoost models were consistently more accurate than the null and historical models for all forecast time horizons. For 1-week ahead predictions across test sets, the mMAE of the XGBoost model with an extending training window was reduced by 78% on average compared to the null model. Although the mMAE increased with longer prediction horizons, XGBoost models showed a 62% reduction in mMAE compared to the null model for 4-week ahead predictions. Our results highlight the potential utility of machine learning methods in forecasting infectious disease incidence when that incidence is defined as an ordinal variable. In particular, the XGBoost model can be easily extended to include more features, thus capturing complex patterns and improving forecast accuracy. Given that many natural extreme phenomena, such as floods and earthquakes, are often described on an ordinal scale when informing planning and response, these results motivate further investigation of using similar scales for communicating risk from infectious diseases.
Adaptive simulated annealing for designing finite-precision PID controller structures

Many control applications pose optimisation problems with multimodal and nonsmooth cost functions. Gradient methods are ineffective in these situations. The adaptive simulated annealing (ASA) offers a viable optimisation tool for tackling these difficult constrained optimisation problems. We demonstrate the effectiveness of the ASA using an application, designing finite-precision PID controller structures with maximum stability robustness measure. The sparseness issue of controller structures is also discussed, and it is shown that the ASA can cope with this kind of constraints easily.
Ne IX and Ne X spectra on the JET tokamak

Observations of H-like Ne x and He-like Ne IX soft X-ray emission line spectra have been made on the JET (Joint European Torus) tokamak. Recently calculated electron impact excitation rates for He-like neon are used in the derivation of the electron temperature sensitive line ratios G=((x+y+z)/w), R1=(1s3p1P1 to 1s2 1S0/w Lyalpha /w, and the electron density sensitive ratio R=(z/(x+y)), where w, x, y and z are the resonance line (1s2p 1P1 to 1s21S0), intercombination (1s2p3P2,1 to 1s2 1S0) and forbidden lines (1s2s3S1 to 1s21S0) respectively and Lyalpha is the H-like Lymanalpha , transition. Extensive modelling is carried out to allow for non-coronal conditions due to diffusion effects in these calculations, which are compared with experimental ratios from JET, where independent temperature and density measurements are available. Departures from equilibrium are found for both ohmic and additionally heated plasmas, resulting in significant changes to the G and Lyalpha /w ratios. The R ratio is approaching its upper density limit and is relatively unaffected by non-coronal conditions. Good agreement between the experimental and calculated ratios is found, giving an indication of the accuracy of the combination of the atomic data and transport employed in the calculations.
Structure and magnetic properties of iron-based cyanide compounds

The M/sub 1.5/[Fe(CN)/sub 6/]/spl middot/zH/sub 2/O powders with M=Ni, Co, Cu and Zn and z=4-7 were prepared by co-precipitation. A structural change was found after heat treatment at a temperature in the range of 100-200/spl deg/C. Mossbauer and magnetic measurements have shown that the Fe/sup III/-CN-M/sup II/ state was the major structure in the co-precipitated form, while the Fe/sup II/-CN-M/sup III/ bond was formed in the annealed samples. The stable Fe/sup II/-CN-M/sup III/ state could convert into a metastable Fe/sup III/-CN-M/sup II/ state accompanied by two peaks in UV-visible spectra. A broad peak was observed in the photo-luminescence spectra, indicating the potential for optical applications.
Particle and magnetic field properties of the Saturnian magnetosheath: Presence and upstream escape of hot magnetospheric plasma

We analyze plasma, energetic particle, and magnetic field data from all available Cassini passes through the Saturnian magnetosheath between July 2004 and July 2011 and provide a statistical overview of particle and field properties. The results show that magnetosheath plasma has an average number density of ~0.1 cm−3 and a temperature of ~300 eV. The measured magnetic field strength is ~1 nT, and the plasma beta is in the range of 10 to 100. The prevailing flow and magnetic field configuration is close to that theoretically expected, with flow speed values of ~200 km/s. Compositional data reveal that although at low energies (few keV) there is a strong presence of water group ions (W+) forming localized structures we refer to as W+ “islands” that travel downstream convected in the plasma flow. Under average magnetic field conditions in the Saturnian magnetosheath, the kinetic properties of these hot W+ ions can enable escape upstream from the bow shock. Based on the measured particle and field distributions and the modeled bow shock and magnetopause positions, we describe the energetic ion escape as a function of energy and pitch angle and successfully predict the energy distribution of the escaping W+ ions. Comparison with the ion spectra measured in the nearby solar wind confirms that the suggested escape mechanism due to large ion gyroradii is sufficient to explain the observed leakage of heavy energetic ions upstream from the Saturnian bow shock.
Spin transfer switching of current-perpendicular-to-plane giant magnetoresistance with various Gd-Fe free-layer compositions

We have investigated the spin transfer switching (STS) properties of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with various compositions of Gd-Fe free-layers for magneto-optical light modulator applications, whereby iron (Fe) concentrations are varied from 72.5 to 80.3 at. %. Switching current densities decreased dramatically with increases in Fe concentration within the Gd-Fe compound. The switching current density (Jc0) for a device with composition Gd Fe80.3 at. % was 20.5 MA/cm2, which is more than eight times smaller than that for devices with composition Gd Fe72.5 at. %. This reduction in switching current can be attributed to a decrease in the effective perpendicular anisotropy in Fe-richer Gd-Fe compounds.
Modified Snowplow Model for Coaxial Plasma Accelerators

In order to explain previously observed deviations of measured plasma velocities from velocities predicted by computer solutions based on a snowplow model, the experimental and computer data are here extended over a much wider range of electrode configurations, capacitor potentials, and gas densities in the shock tube. At low densities the experimental velocity curves fall below the predicted curves because of material evaporated from insulation and electrodes. At high gas densities the experimental velocity curve for the largest center electrode coincides with the predicted curve, but for center electrodes of successively smaller diameter the measured curves lie progressively farther above, but parallel to, those predicted, up to a factor of 5.5 times for the smallest electrode used. These results are explainable in terms of a modified snowplow model postulating an effective annular region adjacent to the center electrode, whose thickness is of the same order as the electrode radius, such that the force .
Simple analytical method to estimate the influence of liquids viscosity on Love wave chemical sensors

In this paper a simple analytical model for a multilayer Love wave device is proposed. This model allows to calculate the phase velocity of the wave with and without sensitive coating in contact with a Newtonian liquid. Experimental tests have been undertaken in order to validate theoretical results. For a biological detection application, the influence of the sensitive coating and liquid parameters on the gravimetric sensitivity is studied.
The problem of false discoveries from a metrological point of view

Valid inference drawn from analysis of experimental results needs scientific grounds, whereas conclusions based on statistical significance tests or hypothesis testing may be problematic, especially when dealing with a multiplicity of tested hypotheses, as in experiments performed on bio-molecules. The problem of false discovery rate is focused in the present paper, aiming at eliciting application of sound criteria for rejection/acceptance of hypotheses and related methods of uncertainty characterisation.