Miracle-dz/UniFAR-FTUs huggingface dataset:
Bending and axial strain dependence of the critical current in superconducting BSCCO tapes

A comparison is made between the critical current (Ic) versus bending strain and axial strain of superconducting multi-filamentary Bi2Sr2Ca2Cu3Ox (Bi-2223) AgMg sheathed tapes. For the bending strain measurement the tape is sandwiched between a curved base and cover plate. Six sets of bending plates introduce bending strains ranging from 0% to 1.0%. The measurements show a slight decrease in Ic after the first bending step after which the degradation becomes more pronounced. The Ic in a bent conductor is calculated assuming a linear axial strain profile inside the conductor. For this calculation the Ic degradation determined in an axial compression and elongation experiment is used. The model predicts an immediate decrease of Ic, caused by the compressive strain dependence. There is a good agreement (within 5%) between the measured data and the calculated values. Based on this good agreement it can be concluded that a possible shift in the neutral line or the formation of additional cracks due to bending has no significant influence on the Ic degradation. It is concluded that the influence of thermal contraction is crucial for a good calculation.
Maximum likelihood estimation of bivariate logistic models for incomplete responses with indicators of ignorable and non‐ignorable missingness

Summary. Missing observations are a common problem that complicate the analysis of clustered data. In the Connecticut child surveys of childhood psychopathology, it was possible to identify reasons why outcomes were not observed. Of note, some of these causes of missingness may be assumed to be ignorable, whereas others may be non‐ignorable. We consider logistic regression models for incomplete bivariate binary outcomes and propose mixture models that permit estimation assuming that there are two distinct types of missingness mechanisms: one that is ignorable; the other non‐ignorable. A feature of the mixture modelling approach is that additional analyses to assess the sensitivity to assumptions about the missingness are relatively straightforward to incorporate. The methods were developed for analysing data from the Connecticut child surveys, where there are missing informant reports of child psychopathology and different reasons for missingness can be distinguished.
A remark about possible unity of the neutron star and black hole high frequency QPOs

In a series of papers it was discussed,on the basis of phenomenological arguments, whether the high frequency quasiperiodic oscillations (kHz QPOs)observed in the neutron-star and black-hole X-ray sources originate in the same physical mechanism. Recently it was suggested that a general trend seen in neutron star kHz QPOs instead excludes such a uniform origin. Using the example of the atoll source 4U 1636-53 we illustrate that this is not neccesarily true.
Nonlinear analysis of generalized cross‐field current instability

Analysis of the generalized cross-field current instability is carried out in which cross-field drift of both the ions and electrons and their temperatures are permitted to vary in time. The unstable mode under consideration is the electromagnetic generalization of the classical modified-two-stream instability. The generalized instability is made of the modified-two-stream and ion-Weibel modes. The relative importance of the features associated with the ion-Weibel mode and those of the modified-two-stream mode is assessed. Specific applications are made to the Earth's neutral sheet prior to substorm onset and to the Earth's bow shock. The numerical solution indicates that the ion-Weibel mode dominates in the Earth's neutral sheet environment. In contrast, the situation for the bow shock is dominated by the modified-two-stream mode. Notable differences are found between the present calculation and previous results on ion-Weibel mode which restrict the analysis to only parallel propagating waves. However, in the case of Earth's bow shock for which the ion-Weibel mode plays no important role, the inclusion of the electromagnetic ion response is found to differ little from the previous results which treats ions responding only to the electrostatic component of the excited waves.
Subminiature hot-wire sensors: development and use

Subminiature hot-wire sensors have been developed and qualified to measure small-scale turbulent motions. Measurements were made with hot wires having 0.625, 1.25 and 5 mu m nominal diameters and lengths ranging from 50 mu m to 3 mm. The smallest sensor has a spatial resolution about ten times better than typical commercially available probes. The measurements were made in the inner layer of a turbulent boundary layer near a smooth wall where the viscous length scale v/Ur was about 50 mu m. The data show how measurement of time-averaged longitudinal turbulence intensity is dependent on sensor dimensions.
Existence and Stability of Travelling Front Solutions for General Auto-catalytic Chemical Reaction Systems

This paper is concerned with the existence and stability of travelling front solutions for more general autocatalytic chemical reaction systems u t = d u xx − uf (v ), v t = v xx + uf (v ) with d > 0 and d ≠ 1, where f (v ) has super-linear or linear degeneracy at v = 0. By applying Lyapunov-Schmidt decomposition method in some appropriate exponentially weighted spaces, we obtain the existence and continuous dependence of wave fronts with some critical speeds and with exponential spatial decay for d near 1. By applying special phase plane analysis and approximate center manifold theorem, the existence of traveling waves with algebraic spatial decay or with some lower exponential decay is also obtained for d > 0. Further, by spectral estimates and Evans function method, the wave fronts with exponential spatial decay are proved to be spectrally or linearly stable in some suitable exponentially weighted spaces. Finally, by adopting the main idea of proof in [12] and some similar arguments as in [21], the waves with critical speeds or with non-critical speeds are proved to be locally exponentially stable in some exponentially weighted spaces and Lyapunov stable in C unif (ℝ) space, if the initial perturbation of the waves is small in both the weighted and unweighted norms; the perturbation of the waves also stays small in L 1 (ℝ) norm and decays algebraically in C unif (ℝ) norm, if the initial perturbation is in addition small in L 1 norm.
InN grown by migration enhanced afterglow (MEAglow)

InN thin films were grown by a new technique, migration enhanced afterglow (MEAglow), a chemical vapour deposition (CVD) form of migration enhanced epitaxy (MEE). Here we describe the apparatus used for this form of film deposition, which includes a scalable hollow cathode nitrogen plasma source. Initial film growth results for InN are also presented including atomic force microscopy (AFM) images that indicate step flow growth with samples having root mean square (RMS) surface roughness of as little as 0.103 nm in some circumstances for film growth on sapphire substrates. X‐ray diffraction (XRD) results are also provided for samples with a full width half maximum (FWHM) of the (0002) ω‐2θ peak of as little as 290 arcsec. Low pressure conditions that can result in damage to the InN during growth are described.
Floating potential perturbations due to micrometeoroid impacts: Theory and application to S/WAVES data

In situ observation of dust grains from various origins is routinely performed by space missions equipped with radio instruments. These measurements consist in observations of voltage pulses or their spectral signature. It has for long been proposed that one of the mechanisms able to produce these pulses is the collection by the spacecraft of electric charges generated by impact ionization. Here for the first time, a complete theoretical model of how pulses are generated by charge collection is proposed. In the solar wind at 1 AU, the pulses are shown to be shaped by local plasma and photoelectron parameters. However, the situation can be different in hotter or denser plasma environments. We use the data provided by the STEREO/WAVES (S/WAVES) radio instrument onboard the twin STEREO spacecraft to validate our model. We find that the observations indeed strongly support the theory. The proposed model is an important step forward, since it makes it possible to reproduce the shape, timescales, and amplitudes of pulses generated by dust impacts in various space environments. Such a model can be used to infer the dust detection abilities of radio instruments onboard different spacecraft and can help the design of dust detection optimized radio instruments for future missions.
Nonlinear vibrations and chaos in gongs and cymbals

This paper summarizes some results obtained in the last few years for the modeling of nonlinear vibrating instruments such as gongs and cymbals. Linear, weakly nonlinear and chaotic regimes are successively examined. A theoretical mechanical model is presented, based on the nonlinear von Karman equations for thin shallow spherical shells. Modal projection and Nonlinear Normal Mode (NNM) formulation leads to a subset of coupled nonlinear oscillators. Current developments are aimed at using this subset for sound synthesis purpose.
The structure of detonation waves in supernovae

La theorie de la detonation gazeuse est appliquee aux ondes de detonation thermonucleaires dans les supernovae. La structure des ondes de choc intenses est consideree dans un plasma degenere et dense. Le taux du transfert d'energie des ions aux electrons est calcule pour un plasma de degenerescence electronique arbitraire et on montre que le chauffage hors equilibre des ions n'est pas important pour les reactions nucleaires. La structure 1D stationnaire des ondes de detonation dans les melanges C+O et dans 4 He est calculee pour des densites 10 6 a 3×10 9 gcm ―3
Selective withdrawal from a finite rectangular tank

The time development of two-dimensional fluid motion induced by a line sink in a rectangular, density stratified reservoir with a free surface is given. It is shown that the initiation of such a sink gives birth to a spectrum of internal expanding shear fronts with a progressively decreasing vertical wavelength. These fronts move out from the sink and travel towards the far wall, where they are reflected. This process ceases once the front with a vertical wavelength equal to the steady withdrawal-layer thickness has reached the end wall. The fronts so introduced continue to move back and forth, expanding to standing waves if the viscosity of the fluid is small enough. The evolution and nature of the withdrawal layer are shown to depend critically on the relative magnitude of the convective inertia and viscous forces, the number of reflexions from the rear wall and the Prandtl number.
Phase resolved optical spectroscopy of the compact X-ray binary 2A 1822–371

The optical, X-ray, and ultraviolet emissions of the X-ray system 2A1822-371 are modulated with a period of 5.57 hr. The 5.57 hr modulation is believed to reflect orbital motion about a mass donating companion star. The modulation at high energies is caused by the combined effects of an occultation by the companion and by a bulge on the accretion disk. The present investigation is concerned with an extension of the study of 2A1822-371, taking into account medium resolution optical spectroscopy of the system covering the 5.57 hr cycle. Broad shallow absorption lines are observed in the optical spectrum of 2A1822-371. These lines are similar to the rotationally broadened lines which are found in the spectra of disk accreting cataclysmic variables. Their presence in 2A1822-371 is, therefore, strong confirmation that it is a disk accreting star. The He II 4686 A and H-alpha emission lines have a breadth comparable to the absorption lines at all phases in the 5.57 hr cycle.
The discovery rate of new comets in the age of large surveys. Trends, statistics, and an updated evaluation of the comet flux

Abstract We analyze a sample of 58 Oort cloud comets (OCCs) (original orbital energies x in the range 0 < x < 100, in units of 10−6 AU−1), plus 45 long-period comets with negative orbital energies or poorly determined or undetermined x, discovered during the period 1999-2007. To analyze the degree of completeness of the sample, we use Everhart's (1967 Astr. J 72, 716) concept of “excess magnitude” (in magnitudes × days), defined as the integrated magnitude excess that a given comet presents over the time above a threshold magnitude for detection. This quantity is a measure of the likelihood that the comet will be finally detected. We define two sub-samples of OCCs: 1) new comets (orbital energies 0 < x < 30) as those whose perihelia can shift from outside to the inner planetary region in a single revolution; and 2) inner cloud comets (orbital energies 30 ≤ x < 100), that come from the inner region of the Oort cloud, and for which external perturbers (essentially galactic tidal forces and passing stars) are not strong enough to allow them to overshoot the Jupiter-Saturn barrier. From the observed comet flux and making allowance for missed discoveries, we find a flux of OCCs brighter than absolute total magnitude 9 of ≃0.65 ± 0.18 per year within Earth's orbit. From this flux, about two-thirds corresponds to new comets and the rest to inner cloud comets. We find striking differences in the q-distribution of these two samples: while new comets appear to follow an uniform q-distribution, inner cloud comets show an increase in the rate of perihelion passages with q.
Quantum entanglement in helium

We compute the entanglement of the ground state and several singlet and triplet excited states of the helium atom using high-quality, state-of-the-art wavefunctions. The behaviour of the entanglement of the helium eigenstates is similar to that observed in some exactly soluble two-electron systems. In particular, the amount of entanglement exhibited by the eigenstates tends to increase with energy.
Townsend's first ionization coefficients in crossed electric and magnetic fields in nitrogen

Townsend's first ionization coefficient (αT) in crossed electric and magnetic fields has been measured in nitrogen over the range of 140 ≤ E/p ≤ 360 volts cm−1 torr-1 and E/p ≤ 650 Oe torr−1. A coaxial cylinder geometry has been employed to avoid diffusion losses in the Ē. × H¯ direction. The initial photoelectric current is obtained by making the ultra-violet radiation obtained in an auxiliary glow discharge fall on the cathode of the coaxial cylinder geometry. Prebreakdown currents in the range of 10−12 − 10−9 amps are measured using the pressure variation technique of Townsend's experiment. The results of Bagnall and Haydon (1965), and Heylen and Bunting (1969) overlap with the present results over a relatively small range of E/p and E/p. Using the equivalent pressure concept the electron molecule collision frequency γ has been derived for the above range of E/p and E/p. It has been observed that γ changes with E/p at a constant E/p and also that γ changes as a function of E/p at a constant E/p. The tra.
Bi-skew braces and Hopf Galois structures

We define a bi-skew brace to be a set $G$ with two group operations $\star$ and $\circ$ so that $(G, \circ, \star)$ is a skew brace with additive group $(G, \star)$ and also with additive group $(G, \circ)$. If $G$ is a skew brace, then $G$ corresponds to a Hopf Galois structure of type $(G, \star)$ on any Galois extension of fields with Galois group isomorphic to $(G, \circ)$. If $G$ is a bi-skew brace, then $G$ also corresponds to a Hopf Galois structure of type $(G, \circ)$ on a Galois extension of fields with Galois group isomorphic to $(G, \star)$. Many non-trivial examples exist. One source is radical rings $A$ with $A^3 = 0$, where one of the groups is abelian and the other need not be. The left braces of degree $p^3$ classified by Bachiller are bi-skew braces if and only they are radical rings. A different source of bi-skew braces is semidirect products of arbitrary finite groups, which yield many examples where both groups are non-abelian, and a skew brace proof of a result of Crespo, Rio and Vela that if $G = H\rtimes J$ is a semidirect product of finite groups, then a Galois extension of fields with Galois group $G$ has a Hopf Galois structure of type $H \times J$.
Robust adaptive non-rigid image registration based on joint salient point sets in the presence of tumor-like gross outliers

Image registration is a process of creating correspondence between a pair of images. In some situations, the physical one-to-one correspondence may not exist due to the presence of "outlier" objects (called gross outliers) that appear in one image but not the other. In this paper, a novel robust method is presented to address the problem of tumor-like gross outliers in non-rigid image registration. First, two salient point sets are extracted from the two images to be registered, and classified by means of clustering analysis which is based on Gaussian mixture models and expectation-maximization (EM) algorithm. Then by means of joint saliency map that represents the joint salient regions of the overlapping volume of the two images, the regions including tumor-like gross outliers could be automatically recognized. After screening out of salient points and elimination of outlier points, some stable control points that well represent the corresponding structures within the joint salient regions of the two images could be obtained. By iteratively finding correspondences between the control points in the joint salient regions, the smooth deformation field is approximated based on radial basis functions (RBFs) with compact support until the convergence to the steady-state solution is achieved. Experimental results show that the proposed method is able to recover local deformation caused by tumor resection in brain.
Pair-particle dynamics and microstructure in sheared colloidal suspensions:Simulation and Smoluchowski theory

The Smoluchowski equation (SE) approach reduced to pair level provides an accepted method for analysis of the pair microstructure, i.e., the pair distribution function g(r), in sheared colloidal suspensions. Under dilute conditions, the resulting problem is well-defined, but for concentrated suspensions the coefficients of the pair SE are unclear. This work outlines a recently developed theoretical approach for analytical and numerical study of the pair SE for concentrated colloidal suspensions of spheres in shear flow, and then focuses upon evaluation of coefficients and related properties of the problem from Stokesian Dynamics simulation, over a wide range of particle volume fraction, ϕ, and Peclet number (ratio of shear to Brownian motion). The pair distribution function determined from the SE theory is in generally good agreement with Stokesian Dynamics, as are the computed viscosity and normal stresses of the material. The primary focus of the work is to consider the pair relative velocity predicted .
MEASUREMENTS AND PREDICTIONS OF THE PHASE VELOCITY AND ATTENUATION COEFFICIENT IN SUSPENSIONS OF ELASTIC MICROSPHERES

The phase velocities and attenuation coefficients for suspensions of narrowly sized polymer microspheres are reported over a broadband spectrum from 3 to 30 MHz. The six suspensions used in this work contain microspheres with respective average diameters near 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, and 100 μm. The results of these measurements are compared with theoretical expressions for the phase velocity and attenuation coefficient derived from the scattering properties of an elastic sphere in water using the weak scattering limit of the Waterman and Truell dispersion relation [J. Math. Phys. 2, 512–537 (1961)]. This single-scattering limit of the theory is found to be sufficient for predicting the ultrasonic transport properties of these suspensions to a considerable degree of accuracy.
Temperature behavior of CLYC/MPPC detectors

He-3 tubes are the most popular thermal neutron detectors. They are easy to use, have good sensitivity for neutron detection, and are insensitive to gamma radiation. Due to low stockpiles of the He-3 gas, alternatives are being sought to replace these devices in many applications. One of the possible alternatives to these devices are scintillators incorporating isotopes with high cross-section for neutron capture (e.g. Li-6 or B-10). Cs2LiYCl6:Ce (CLYC) is one of the scintillators that recently has been considered for neutron detection. This material offers good detection efficiency (~80%), bright response (70,000 photons/neutron), high gamma ray equivalent energy of the neutron signal (>3MeV), and excellent separation between gamma and neutron radiation with pulse shape discrimination. A He-3 tube alternative based on a CLYC scintillator was constructed using a silicon photomultiplier (SiPM) for the optical readout. SiPMs are very compact optical detectors that are an alternative to usually bulky photomultiplier tubes. Constructed detector was characterized for its behavior across a temperature range of -20°C to 50°C.
Room‐temperature heterojunction laser diodes from vapor‐grown In1−xGaxP/GaAs structures

Vapor‐grown epitaxial structures of In0.5Ga0. 5P/GaAs have yielded heterojunction laser diodes with room‐temperature threshold current densities as low as 8000 A/cm2 for a 2.5‐μm GaAs laser cavity width. Differential external quantum efficiencies as high as 30% have been attained. Measurements suggest the existence of internally ``trapped'' laser modes due to the large refractive‐index discontinuity at the In0.5Ga0. 5P–GaAs interfaces.
The vorticity jump across a shock in a non-uniform flow

The vorticity jump across an unsteady curved shock propagating into a two-dimensional non-uniform flow is considered in detail. The exact general expression for the vorticity jump across a shock is derived from the gasdynamics equations. This general expression is then simplified by writing it entirely in terms of the Mach number of the shock MS and the local Mach number of the flow ahead of the shock MU. The vorticity jump is very large at places where the curvature of the shock is very large, even in the case of weak shocks. Vortex sheets form behind shock-shocks (associated with kinks in the shock front). The ratio of vorticity production by shock curvature to vorticity production by baroclinic effects is O(½(γ−1)M2U), where γ is ratio of specific heats, which is very small if the flow ahead of the shock is only weakly compressible. If, however, the tangential gradient along the shock of M2U is large then baroclinic production is significant; this is the case in turbulent flows with large gradients of turbulent kinetic energy ½M2U. The vorticity jump across a weak shock decreases in proportion to shock intensity if the flow ahead of the shock is rotational, rather than in proportion to the cube of shock intensity as is often assumed, and thus is not negligible. It is also shown that vorticity may be generated across a straight shock even if the flow ahead of the shock is irrotational. The importance of the contribution to the vorticity jump by non-uniformities in the flow ahead of the shock has not been recognized in the past. Examples are given of the vorticity jump across strong and weak shocks in a variety of flows exhibiting some properties of turbulence.