Miracle-dz/UniFAR-FTUs huggingface dataset:
Convergence of quasi-stationary to stationary distributions for stochastically monotone Markov processes

It is shown that if a stochastically monotone Markov process on [0,∞) with stationary distribution H has its state space truncated by making all states in [B,∞) absorbing, then the quasi-stationary distribution of the new process converges to H as B →∞.
Hα Stokes V/I Features Observed in a Solar Active Region

We carried out an imaging polarimetry observation of active region NOAA 10596 at 9–11 wavelengths around the Hα line with a ferroelectric liquid-crystal polarimeter during 2004 April 20–26. The latitude of the region was S8 ◦ , and it passed the central meridian on April 23. On the basis of this observation, the Stokes V/ Ifeatures of the active region in Hα, which are expected to indicate the chromospheric longitudinal magnetic field, were revealed as follows: (1) There is persistent weakening (sometimes reversal) of the Stokes V/ I signal at the center of the umbra. This is not due to the actual weakening of the magnetic field strength, but probably due to the peculiarity of the atmospheric structure of the umbral chromosphere. (2) The peak wavelengths of the Stokes V/ Iprofile of the plages and that of the sunspot are systematically different from each other and, therefore, it is difficult to apply the weak-field approximation to estimate the chromospheric magnetic field strength. Both of these results mean that an estimation of the chromospheric magnetic field on the basis of the Hα polarimetry is not straightforward, and that an inversion considering the atmospheric structure in the chromosphere is essentially important.
Mathematical Analysis for MHD Flow of Blood in Constricted Arteries

Abstract The unsteady oscillatory magneto-hydrodynamic flow of blood in small diameter arteries with mild constriction is analyzed, blood being modelled as a Herschel-Bulkley fluid. Finite difference method is employed for solving the associated initial boundary value problem. Explicit finite difference schemes for velocity distribution, flow rate, skin friction and longitudinal impedance to the flow are obtained. The effects of pressure gradient, yield stress, magnetic field, power law index and maximum depth of the stenosis on the aforesaid flow quantities are discussed through appropriate graphs. It is found that the velocity and flow rate decrease and the skin friction and longitudinal impedance to flow increase with the increase of the magnetic field parameter. It was recorded that the flow rate increases and the skin friction decreases with the increase of the phase angle. It was also noted the skin friction and longitudinal impedance to flow that increase almost linearly with the increase of maximum depth of the stenosis. The estimates of the increase in the longitudinal impedance to flow and skin friction are increased considerably by the presence of the magnetic field.
Numerical Simulations of the Rebound Shock Model for Solar Spicules

Using time-dependent numerical simulations, the proposed rebound shock mechanism for spicules has been examined. At temperatures above a critical value, T(c), the radiation is characteristic of the conditions in the optically thin corona and near optically thin transition region. When T less than T(c), the atmosphere has a radiative cooling time, tau(rad) characteristic of chromosphere. The spicule is initiated with a quasi-impulsive force in the low chromosphere, which drives a train of upward propagating rebound shocks along the rigid magnetic flux tube. These shocks then move the transition region upward. The material below the displaced transition region has temperatures and densities similar to those of spicules when T(c) = 20,000 K or more and tau(rad) = 500 s or more, but not when T(c) = 10,000 K, and probably not when tau(rad) = 100 s. For all the cases where the cross sectional area diverges rapidly with height, the upward velocity of the transition region is less than that of spicules. Moreover, the maximum height is less than that of average spicules. Taller, higher velocity spicules result when the magnetic field cross sectional area is constant. In all cases, the rebound shock mechanism produces substantial motions and temperature and densitymore » variations in chromospheric and transition region material. It is suggested that this may be a partial explanation for the continuous dynamic state of the lower solar atmosphere. 30 refs.« less
Radiative Lifetimes in Sc I-Sc III

We have studied the spectra of scandium (600-6 000 ? ) with the beam-foil method. In the v.u. v. a few previously unreported Sc III transitions appeared, as well as several well-known Sc III multiplets, whereas most lines in the air region were ascribed to earlier classified Sc I and Sc II transitions. We also measured the mean lifetimes of 20 excited Sc I-Sc III levels and generally found good agreement with previous theoretical calculations and emission measurements.
Higher Order Statistics from the Edinburgh/Durham Southern Galaxy Catalogue Survey. I. Counts in Cells

Counts in cells are used to analyze the higher order properties of the statistics of the Edinburgh/ Durham Southern Galaxy Catalogue Survey (EDSGC). The probability distribution is obtained from an equal area projection source catalog with infinite oversampling over the range 0. °015-2°. The factorial moments of the resulting distribution and the sN's characterizing the non-Gaussian nature of the distribution are extracted. These results are compared to previous results from the Automatic Plate Measuring Facility (APM) survey and to theoretical results from perturbation theory. The deprojected three-dimensional values corresponding to the sN's are also determined. We find that the three-dimensional values match the scaling relation for strongly nonlinear clustering found in N-body simulations remarkably well, which suggests that the galaxies are reliable tracers of the underlying mass distribution.
The arithmetic mean method for solving essentially positive systems on a vector computer

This paper is concerned with a generalization of the arithmetic mean method developed in [3] for solving large “essentially positive” dynamic systems which are asymptotically stable. This method is well suitable for parallel implementation on a multiprocessor system that can execute concurrently different tasks on a few vector processors with shared central memory, such as the CRAY X-MP. A high-level parallelism among independent tasks is obtained using the Cray multitasking. The consistency and the stability of the method are analysed.
Dependence of magnetic susceptibility on stress in textured polycrystalline Fe81.6Ga18.4 and Fe79.1Ga20.9 Galfenol alloys

Magnetization and magnetostriction measurements in constant tension and compression as a function of applied magnetic field are reported for ⟨100⟩ oriented, textured polycrystalline Fe81.6Ga18.4 and Fe79.1Ga20.9 Galfenol alloys. The susceptibility change with stress, or sensitivity, is maximum at zero field for both alloys. The greatest sensitivity is observed for the 18.4 at. % Ga alloy between −10 and +20 MPa, where domain wall motion dominates. The sensitivity is greater for the 20.9 at. % Ga alloy than for the 18.4 at. % Ga alloy below −15 MPa (domain rotation region). The difference in behavior is attributed to a difference in the anisotropy coefficient.
Stall Warning by Blade Pressure Signature Analysis

At low mass flow rates, axial compressors suffer from flow instabilities leading to stall and surge. The inception process of these instabilities has been widely researched in the past---primarily with the aim of predicting or averting stall onset. In recent times, attention has shifted to conditions well before stall and has focused on the level of irregularity in the blade passing signature in the rotor tip region. In general, the irregularity increases in intensity as the flow rate through the compressor is reduced. Attempts have been made to develop stall warning/avoidance procedures based on the level of flow irregularity, but little effort has been made to characterize the irregularity itself, or to understand its underlying cause. Work on this project has revealed for the first time that the increase in irregularity in the blade passing signature is highly dependent on both tip-clearance size and eccentricity. In a compressor with small, uniform, tip-clearance, the increase in blade passing irregularity that accompanies a reduction in flow rate will be modest. If the tip-clearance is enlarged, however, there will be a sharp rise in irregularity at all circumferential locations. In a compressor with eccentric tip-clearance, the increase in irregularity will only occur in the part of the annulus where the tip-clearance is largest, regardless of the average clearance level. In this paper, some attention is also given to the question of whether the irregularity observed in the prestall flow field is due to random turbulence or to some form of coherent flow structure. Detailed flow measurements reveal that the latter is the case. From these findings, it is clear that a stall warning system based on blade passing signature irregularity would be difficult to implement in an aero-engine where tip-clearance size and eccentricity change during each flight cycle and over the life of the compressor. © 2013 American Society of Mechanical Engineers.
Basic properties of solar wind MHD turbulence near 0.3 AU analyzed by means of Elsässer variables

Magnetic field and plasma data, obtained by the Helios 1 and 2 spacecraft in the solar wind near 0.3 AU during the years 1975 to 1976, have been analyzed by calculating 12 kinds of spectra related to the Elsasser variables, δZ+ = δV + δVA, and δZ− = δV − δVA, where δV and δVA are the bulk velocity and Alfven velocity fluctuations, respectively. For small amplitude Alfven waves the fluctuation variable δZ+ simply relates to outward propagation and δZ− to an inward sense of propagation, if the ambient magnetic field B0 is directed inward. The frequency range analysed in this paper is 6×10−6 Hz to 6×10−3 Hz. It is found that (1) the autocorrelation length for δZ− is much larger than for δZ+ in both the high-speed and low-speed wind. (2) The power spectra of δZ−, especially in high-wind speed, are steeper in the low-frequency range and flatten in the high-frequency range. (3) In the low-frequency range, the power spectra for the components of δZ+ tend to be isotropic with respect to the three polarization directions, while the spectra of δZ− are dominated by the radial component. In the high-frequency domain, the spectra of both δZ+ and δZ− are dominated by the transverse component in high-speed wind and are more isotropic in low-speed wind. (4) The spectra related to the residual energy or the cross-correlation in low-speed flows have a power law with the slope near to −5/3. However, in high-speed flows the corresponding data are widely distributed in a cloud of points with an upper envelope near to the spectrum of δZ−. The origin of all these spectra and their importance for the solar wind physics have also been discussed. Several generation mechanisms are suggested as candidates. In the flat part of e− spectrum, the fluctuations may be generated by non-local (in wave number space) interactions with the low-frequency part of the e+ spectrum, or just by parametric decay of the high-frequency part of the e+ spectrum. The steep part of e− (f) may be related to small-scale stream tubes, or be influenced by pressure waves, nonlinear cascading, and the interaction with the outgoing Alfven waves.
Numerical Simulation of Two‐Dimensional Turbulence

The two‐dimensional incompressible Navier‐Stokes equations are numerically integrated in order to test the validity of Kraichnan's predictions on the structure of two‐dimensional turbulence. The numerically simulated turbulence is produced by an artificial forcing function, constructed from a randomly varying set of Fourier modes lying within a narrow spectral band near scalar wavenumber ke. For the case of turbulence maintained by a constant rate of energy injection, Kraichnan predicts the development of two power‐law energy spectra, a k−5/3 range for frequencies less than ke, and a k−3 range for those greater than ke. The numerical results are consistent with these predictions, although truncation and aliasing errors restrict the useful spectral range of the calculations to less than that desirable for a fully satisfactory test. The predictions and results are apparently relevant to several areas of geophysical fluid dynamics and to the correct interpretation of other numerical simulation experiments.
Simultaneous temperature and velocity measurements in the plane of symmetry of a transitional turbulent spot

Simultaneous measurements of the longitudinal velocity U, normal velocity V, and temperature T have been made in turbulent spots generated in a slightly heated laminar boundary layer. The measurements were made in the plane of symmetry of the spot at several streamwise stations downstream of the spot-producing spark. Ensemble averages of U, V and T, obtained relative to the leading edge of the spot, are presented in terms of disturbances relative to the unperturbed values in the laminar flow. Ensemble-averaged disturbances of U, V and T in the outer part of the spot are consistent with a picture of a relatively large vortical structure with a spanwise vorticity in the same sense as that of the laminar flow. A rather dominant feature of these distributions is the large negative disturbance in V and U near the leading edge in the outer part of the spot; associated with this disturbance is a positive perturbation in T. The terms contributing to the ensemble-averaged values of UV, UT and VT are obtained and discussed. In the case of UV, contributions by the disturbance are found to be of the same order as those by the random turbulence superposed on the disturbance. For VT, the disturbance appears to play a more dominant role in the transfer of heat. The conical property of the spot is tested for disturbance temperature and velocity fields by comparing contours, at three streamwise stations, of the velocity and temperature disturbances using the co-ordinates introduced by Cantwell, Coles & Dimotakis (1978). The results show that the conical transformation, which was found to be a good approximation for the full velocity field, is not an accurate representation for the disturbance fields of velocity and temperature measured relative to laminar values. An alternative viscous transformation represents more accurately the disturbance fields. Features of the turbulence within the spot are compared with those obtained in a fully turbulent boundary layer.
Angular distribution of radiation from low-mass X-ray binaries

The angular distribution of the X-ray emission from low-mass binary systems has been investigated under the assumption that an optically thin, geometrically thick disk developes in the vicinity of accreting neutron stars. Through scattering in the extended inner disk, radiation from the boundary layer is shown to be collimated in the direction perpendicular to the disk plane, and radiation from the stellar surface is enhanced in the same direction as a result of the reflection of photons incident upon the disk surface. The results suggest mass-radius relations for the burst sources EXO 0748-676 and 4U/MXB 1636-53 in the 2.2-3.4 Schwarzschild radius range. Under these conditions, the persistent emission is dominated by the radiation originating from the boundary layer and is then reprocessed in the inner disk. 26 references.
Estimating the Mean of an Increasing Stochastic Process at a Censored Stopping Time

Abstract Data often come in the form of a longitudinal series, say N(·), whose observation has been “stopped” either by a terminal event U (e.g., death) or censoring event C (e.g., lost to follow-up). When N(·) is not deterministic, it is generally not possible to use standard survival analysis tools (e.g., the Kaplan-Meier estimator) to consistently estimate functionals of the distribution of N(U) because of “induced” informative censoring. Various seemingly unrelated estimators recently have been proposed to handle this difficulty within the context of specific problems, ranging from the analysis of quality-adjusted survival data to recurrent event data to lifetime medical cost data. In this article I consider a general framework containing each of these specific examples as a special case, propose a class of estimators for the mean of the stopped longitudinal process, and establish the asymptotic properties of this class of estimators. Connections between the aforementioned estimators are established, and questions related to asymptotic relative efficiency of the various estimators are addressed. Based on these results, I propose some new estimators with finite-sample optimality properties. Finally, I investigate the utility of the proposed estimators in two simulated examples, and discuss potential extensions of this work.
A Variational Approach to Optimal Two-Treatment Crossover Designs: Application to Carryover-Effect Models

Abstract A variational method is used to obtain sufficient conditions for an optimal two-treatment, p-period design, given a repeated-measures model with arbitrary within-subject covariance. The design minimizes the variance of the estimator of treatment differences over all possible allocations of N subjects to the 2 p possible treatment sequences. The method is applied to a model that includes carryover effects. When subject effects are random with equicorrelated observations, designs are optimal if they are (a) strongly balanced; (b) uniform on the rows; and (c) either uniform on the subjects p is even and greater than 2, or uniform on the first p — 1 periods if p is odd. For two periods the optimal design is AB, BA, AA, BB. The same designs are optimal when baseline measurements are obtained in each period. Baseline observations improve efficiency considerably for p = 2, only slightly for p odd, and are of no help for p even and greater than 2. A second model of errors in which a subject's response ha.
The onset of instability in unsteady boundary-layer separation

The process of unsteady two-dimensional boundary-layer separation at high Reynolds number is considered. Solutions of the unsteady non-interactive boundary-layer equations are known to develop a generic separation singularity in regions where the pressure gradient is prescribed and adverse. As the boundary layer starts to separate from the surface, however, the external pressure distribution is altered through viscous—inviscid interaction just prior to the formation of the separation singularity; hitherto this has been referred to as the first interactive stage. A numerical solution of this stage is obtained here in Lagrangian coordinates. The solution is shown to exhibit a high-frequency inviscid instability resulting in an immediate finite-time breakdown of this stage. The presence of the instability is confirmed through a linear stability analysis. The implications for the theoretical description of unsteady boundary-layer separation are discussed, and it is suggested that the onset of interaction may occur much sooner than previously thought.
Sign reversal and light controlled tuning of circular polarization in semimagnetic CdMnSe quantum dots

Circularly polarized luminescence of CdMnSe quantum dots in magnetic fields up to 5 T is studied for nominal Mn concentrations of 0%, 1%, and 2% by using a photoelastic modulator technique. The exciton g factors as well as spin relaxation times were determined from the polarized luminescence taking into account the exciton lifetimes, which were also extracted by means of time-resolved photoluminescence spectroscopy. For quantum dots without Mn and with 2% Mn exciton g factors of −1.62 and +1.32, respectively, were found. The quantum dots with 1% Mn show a vanishing small value of g for small excitation powers. For this structure the polarization properties are dominated by the optical orientation. Interestingly, for the 1% Mn quantum dots with increasing excitation power considerable changes of the polarization and the exciton g factor were observed which are interpreted in terms of heating effects. From the power dependence indirect heating via phonons and above a critical value direct heating due to pho.
Young α-enriched giant stars in the solar neighbourhood

We derive age constraints for 1639 red giants in the APOKASC sample for which seismic parameters from Kepler, as well as effective temperatures, metallicities and [α/Fe] values from APOGEE DR12 (Apache Point Observatory Galactic Evolution Experiment Data Release 12) are available. We investigate the relation between age and chemical abundances for these stars, using a simple and robust approach to obtain ages. We first derive stellar masses using standard seismic scaling relations, then determine the maximum possible age for each star as function of its mass and metallicity, independently of its evolutionary stage. While the overall trend between maximum age and chemical abundances is a declining fraction of young stars with increasing [α/Fe], at least 14 out of 241 stars with [α/Fe] >0.13 are younger than 6 Gyr. Five stars with [α/Fe] ≥0.2 have ages below 4 Gyr. We examine the effect of modifications in the standard seismic scaling relations, as well as the effect of very low helium fractions, but these changes are not enough to make these stars as old as usually expected for α-rich stars (i.e. ages greater than 8–9 Gyr). Such unusual α-rich young stars have also been detected by other surveys, but defy simple explanations in a galaxy evolution context.
Global asymptotic dynamics of gradient-like bistable equations

The dynamics on the global attractors of bistable gradient-like evolution equations are described via a semiconjugacy onto the dynamics of a simple system of ordinary differential equations. The fact that the semiconjugacy is “onto” implies that, given any solution to the ordinary differential equation, there exists a corresponding orbit on the attractor of the evolution equation. It is also shown that these results apply to the damped wave equation, a viscoelastic beam equation, the Fitz–Hugh–Nagumo equations, the Cahn–Hilliard equation, and the phase-field equations. The proofs are based on the Conley index theory.
Quenched magnetic moment in Mn-doped amorphous Si films

Author(s): Zeng, L; Helgren, E; Rahimi, M; Hellman, F; Islam, R; Wilkens, BJ; Culbertson, RJ; Smith, DJ | Abstract: The absence of a Mn local moment was observed in Mn-doped amorphous silicon (a- Mnx Si1-x) films. The magnetic susceptibility obeys the Curie-Weiss law for a wide range of x (5× 10-3 up to 0.175) but with extremely small moment. Magnetization measurements suggest that this behavior occurs because only a small percentage of Mn (Mn2+ states with J=S=5/2) contribute to the magnetization. Thus, the magnetic moments are quenched for the majority of Mn atoms, contrary to the general belief of the existence of a localized Mn moment in Si. X-ray absorption spectroscopy suggests that the quenching of Mn moments is attributed to the formation of an itinerant but Anderson-localized impurity band, forming at x as low as 5× 10-3. © 2008 The American Physical Society.
The Convergence of Biorthogonal Series for Biharmonic and Stokes Flow Edge Problems: Part II

Sufficient conditions are established for the convergence of the biorthogonal series solving edge problems which arise in elasticity and in Stokes flow in cavities. These conditions and those given in Part I, (D. D. Joseph, The convergence of biorthogonal series for biharmonic and Stokes flow edge problems, SIAM, J. Appl. Math., 33(1977), pp. 337–347) include all those which are likely to arise in applications. Examples of conditional convergence of the series to step functions and to ramp functions are presented. Problems previously considered to be intractable to analysis are solved by analysis.