Miracle-dz/UniFAR-FTUs huggingface dataset:
STRUCTURE OF RETROGRADE CIRCUMBINARY ACCRETION DISKS

We evaluate the interactions between a central equal mass binary and a surrounding retrograde circumbinary accretion disk in a three-dimensional, MHD simulation. We find (as widely expected) that the net torque expressed on a retrograde circumbinary disk by the central binary is much (more than two orders of magnitude) smaller than when the disk orbits in the prograde direction. For this reason, unlike the prograde case, there is no “gap” carved out of the retrograde disk, and accreting fluid can travel directly from the disk to the domain of the binary. For the same reason, retrograde disks do not develop the large-amplitude “lumps” generically seen near the inner edges of prograde disks. Although not directly treated in this simulation, the finite extent of accretion disks around the individual masses of the binary can lead to shocks between their outer edges and the circumbinary disk, potentially creating a photon signal modulated at the binary orbital period. The spectra of these shocks should peak in the hard X-ray band as is expected for prograde systems, but retrograde systems would not be expected to display a “notch” in the optical/UV band. Because the disk’s angular momentum is directed oppositely to that of the binary, accretion onto the binary causes a rapid increase in eccentricity. Lastly, we discuss the comparative rates of orbital evolution associated with accretion in prograde and retrograde circumbinary disks, finding that the principal contrast is that e ˙ ? > should be rather greater in the retrograde case.
Electrical characteristics and thermal stability of HfO2 metal-oxide-semiconductor capacitors fabricated on clean reconstructed GaSb surfaces

HfO2/GaSb interfaces fabricated by high-vacuum HfO2 deposition on clean reconstructed GaSb surfaces were examined to explore a thermally stable GaSb metal-oxide-semiconductor structure with low interface-state density (Dit). Interface Sb-O bonds were electrically and thermally unstable, and post-metallization annealing at temperatures higher than 200 °C was required to stabilize the HfO2/GaSb interfaces. However, the annealing led to large Dit in the upper-half band gap. We propose that the decomposition products that are associated with elemental Sb atoms act as interface states, since a clear correlation between the Dit and the Sb coverage on the initial GaSb surfaces was observed.
Spoken Language and Mathematics

Teachers and learners use spoken language in the three part mathematics lesson advocated by the National Numeracy Strategy (NNS). This document recognises the importance of language by emphasising 'the correct use of mathematical vocabulary' in the raising of standards. Research into the use of vocabulary in science suggests that the use of scientific words does not necessarily demonstrate conceptual understanding. Pupils and teachers appear to ascribe different meanings to scientific words because of their relative positions on the novice/expert continuum. To explore whether mathematical words could cause similar problems, data collected from six groups of teachers and learners was subjected to discourse analysis to provide evidence of how spoken language was used and how meaning and understanding were achieved. The implications of the findings on the use of language by both teachers and learners in the NNS mathematics lesson, including vital areas for reflection by teachers, are fully considered.
Hamiltonian, path integral and BRST formulations of the Chern–Simons–Higgs theory in the broken symmetry phase

The Hamiltonian, path integral and BRST formulations of the Chern–Simons–Higgs theory in two-space one-time dimensions are investigated under appropriate gauge-fixing conditions, in the broken (or frozen) symmetry phase, where the phase φ (xμ) of the complex matter field Φ(xμ) carries the charge degree of freedom of the complex matter field and is, in fact, akin to the Goldstone boson.
Fulde-Ferrell-Larkin-Ovchinnikov state in layered superconductors

The phase diagram of a layered superconductor in a large parallel magnetic field is calculated. This includes a calculation of the lower critical field beyond which the superconductor is in the FFLO-state and possesses a spatially modulated order parameter and spin polarization. The order parameter, spin polarization, free-energy density, and phase boundaries of this unconventional superconducting phase are evaluated numerically in the complete B–T plane. The analysis suggests that the transition at the lower critical field is of second order, and not of first order, as previously assumed. The order parameter of the FFLO-state merges continuously into the uniform superconducting state.
Reversibility of trapped hole annealing

Annealing under negative bias of metal-oxide-semiconductor field-effect transistors (MOSFETs) previously irradiated and annealed under positive bias is studied as a function of oxide field and time. Using three different sets of samples ranging from hard to soft, it is possible to observe a considerable reversal of the oxide trapped charge component in the two harder sets and essentially none in the soft set. These results are interpreted in terms of electrons tunneling back and forth from the Si substrate to electron traps associated with the simple oxygen vacancy (an E' center) in the oxide. Some of these compensating electrons do reform the Si-Si bonds broken by the trapped holes. The results are consistent with a large body of previous work. In addition, the data suggest that the energy level of the hole trap is below the valence band edge of Si. >
Vacuum Noise and Stress Induced by Uniform Acceleration Hawking-Unruh Effect in Rindler Manifold of Arbitrary Dimension

This is a comprehensive account of a particular recent development concerning the thermal character inherent in the quantum field as viewed from a uniformly accelerated frame of reference. That is, the power spectrum of the vacuum noise (or the detector-response function) seen by a uniformly accelerated observer in flat spacetimes of arbitrary dimensions is investigated and is shown to exhibit the phenomenon of the apparent inversion of statistics in odd dimensions. Its relation to the thermalization theorem is clarified. Also discussed are the closely related phenomena occurring in the vacuum stress of the Rindler manifold and in the noise seen by a comoving observer in the de Sitter spacetime, as well as those associated with the circular motion in the flat spacetime.
Power Bases in Dihedral Quartic Fields

Abstract A quartic number field,L, is calleddihedralif the normal closure,N, ofLsatisfies Gal(N/ Q )≅D8. We investigate whether or not the ring of integers of such a quartic field has a power basis. When the quadratic subfield ofLis imaginary, the problem is completely solved. When it is real, the same method leads to a solution in many cases. Several numerical illustrations of the method are given.
Noetherian Semigroup Algebras

A complete structural characterization of submonoids S of a polycyclic‐by‐finite group such that the semigroup algebra K[S] over a field K is right noetherian is obtained. It follows that such algebras are also left noetherian. 2000 Mathematics Subject Classification 16P40, 16S36, 20M25 (primary), 20F22, 20C07, 20M10 (secondary).
Nonlinear evolution of large-scale structure in the universe

Using N-body simulations we study the nonlinear development of primordial density perturbation in an Einstein--de Sitter universe. We compare the evolution of an initial distribution without small-scale density fluctuations to evolution from a random Poisson distribution. These initial conditions mimic the assumptions of the adiabatic and isothermal theories of galaxy formation. The large-scale structures which form in the two cases are markedly dissimilar. In particular, the correlation function xi(r) and the visual appearance of our adiabatic (or ''pancake'') models match better the observed distribution of galaxies. This distribution is characterized by large-scale filamentary structure. Because the pancake models do not evolve in a self-similar fashion, the slope of xi(r) steepens with time; as a result there is a unique epoch at which these models fit the galaxy observations. We find the ratio of cutoff length to correlation length at this time to be lambda/sub min//r/sub 0/ = 5.1; its expected value in a neutrino dominated universe is 4(.cap omega.h)/sup -1/ (H/sub 0/ = 100h km s/sup -1/ Mpc/sup -1/). At early epochs these models predict a negligible amplitude for xi(r) and could explain the lack of measurable clustering in the Ly.cap alpha. absorption lines of high-redshift quasars. However, large-scale structuremore » in our models collapses after z = 2. If this collapse precedes galaxy formation as in the usual pancake theory, galaxies formed uncomfortably recently. The extent of this problem may depend on the cosmological model used; the present series of experiments should be extended in the future to include models with . cap omega. <1. « less
Time series modelling of childhood diseases: a dynamical systems approach

A key issue in the dynamical modelling of epidemics is the synthesis of complex mathematical models and data by means of time series analysis. We report such an approach, focusing on the particularly well‐documented case of measles. We propose the use of a discrete time epidemic model comprising the infected and susceptible class as state variables. The model uses a discrete time version of the susceptible–exposed–infected–recovered type epidemic models, which can be fitted to observed disease incidence time series. We describe a method for reconstructing the dynamics of the susceptible class, which is an unobserved state variable of the dynamical system. The model provides a remarkable fit to the data on case reports of measles in England and Wales from 1944 to 1964. Morever, its systematic part explains the well‐documented predominant biennial cyclic pattern. We study the dynamic behaviour of the time series model and show that episodes of annual cyclicity, which have not previously been explained quantitatively, arise as a response to a quicker replenishment of the susceptible class during the baby boom, around 1947.
Switching between polarized modes of a vertical-cavity surface-emitting laser by isotropic optical feedback

Experiments are described that show that polarization of light in a vertical-cavity surface-emitting laser subjected to isotropic optical feedback can jump regularly back and forth between two orthogonal states when the injection current is increased. The polarization-resolved light-current characteristic curves are thus channeled. This effect occurs when the dichroism of the laser is weak enough to allow the effective (isotropic) reflectance to impose the polarization. A comparison of a model introduced by San Miguel [Phys. Rev. A52, 1728 (1995)] and the standard equations indicates that the best description is given when no spin relaxation is included.
Bounded Risk Estimation of the Scale Parameter of a Gamma Distribution in a Two-Stage Sampling Procedure

Abstract A two-stage sampling procedure is developed for estimating the scale parameter β in a gamma distribution Gamma(α, β), with known α, where the risk of an estimator of β is less than from a preassigned number ω(> 0); that is, , 0 < A < ∞ is known. In this article, we provide explicit formulas for the distribution of the total sample size, N m . With this we propose how to determine the parameter B m of the stopping variable so that the risk is uniformly bounded by ω. In the end, the performances of the proposed methodology are investigated with the help of simulations.
NON-LINEAR GALLOPING OF SAGGED CABLES IN 1:2 INTERNAL RESONANCE

The aeroelastic behaviour of a flexible elastic suspended cable driven by mean wind speed, blowing perpendicularly to the cable's plane, is investigated. By applying the Galerkin procedure to the partial differential equations of motion and using an in-plane and an out-of-plane mode as shape functions, a two-d.o. f. model is derived. The discrete equations are coupled through quadratic and cubic terms arising both from geometric and aerodynamic effects. The associated linear frequencies are assumed to be in an almost 1:2 ratio, so that internal resonance occurs. The multiple scale perturbation method is employed to obtain a set of three amplitude modulation equations, whose coefficients depend on the mean wind speed, which is assumed as control parameter. Two perturbative solutions are developed, each based on a different assumption about the order of magnitude of the static displacements, produced by steady state wind forces. Analytical results are then compared with direct numerical integrations of discrete non-linear equations. By performing a bifurcation analysis, the existence of several equilibrium branches is proved. The relative importance of geometric and aerodynamic non-linearities is discussed through simplified models. The influence on critical and postcritical behaviour of several parameters, including geometrical cable parameters, detuning and non-symmetric flow effects, is investigated. The important role played by the steady state forces is highlighted.
Investigation of flow behind vortex generators by stereo particle image velocimetry on a thick airfoil near stall

Stereoscopic Particle Image Velocimetry measurements investigating the effect of vortex generators (VGs) on the flow near stall were carried out in a purpose-built wind tunnel for airfoil investigations on a DU 91-W2-250 profile. Measurements were conducted at Re = 0.9⋅106, corresponding to free stream velocity U∞ = 15 m s−1. The objective was to investigate the flow structures induced by the vortex generators and study their separation controlling behavior on the airfoil. The uncontrolled flow (no VGs) displayed unsteady behavior with separation as observed from large streamwise velocity variations. The corresponding controlled flow (with VGs) showed the same unsteadiness, where the appearance of the vortex structures alternated with a much less separated or even attached boundary layer as also seen in the measured airfoil data: CL = 1.56, CD = 0.116 with VGs and CL = 1.16, CD = 0.135 without. On average, the controlled flow left an attached flow as opposed to the uncontrolled one. Mixing close to the wall, transferring high momentum fluid into the near wall region, was observed, and the hypothesis of variations in the streamwise velocity component in the boundary layer was supported by a Snapshot Proper Orthogonal Decomposition analysis. This analysis also revealed some of the dynamics of the induced vortices. Copyright © 2012 John Wiley & Sons, Ltd.
Oxygen-vacancy-induced green emission and room-temperature ferromagnetism in Ni-doped ZnO nanorods

Single-crystalline Ni-doped ZnO nanorods have been synthesized through a chemical method. The average length and diameter of these nanorods are in the ranges of 400–700 nm and 25–40 nm, respectively. Structural analyses reveal that the Ni-doped ZnO nanorods are of pure wurtzite hexagonal phase and grow along the preferred c-axis direction. X-ray photoelectron spectroscopy (XPS) gives evidence that the Ni dopant is in the +2 valence oxidation state and is uniformly distributed in the nanorods. Full multiple-scattering ab initio calculations of Ni K-edge x-ray absorption near edge structure (XANES) analysis reveal that Ni impurity atoms are substitutionally incorporated into ZnO host without formation of secondary phases (Ni metal and Ni2O3). The comparison of experimental and simulated XANES spectra on Ni K edge shows the presence of the oxygen vacancy (native defect) in the prepared nanorods. Photoluminescence spectrum shows two emission peaks, which are ascribed to near band edge (NBE) transitions and broadened intensive green emission associated with oxygen-vacancy defects. Furthermore, the magnetic measurements reveal that the nanorods exhibit intrinsic room-temperature ferromagnetism. Ferromagnetic ordering is interpreted by the overlapping of polarons mediated through oxygen vacancy based on the bound magnetic polaron (BMP) model.
Investigation of Vortex Shedding and Wake-Wake Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Particle-Image-Velocimetry

The current paper presents a time-resolved experimental flow investigation in a highly loaded transonic gas turbine stage operating continuously under engine representative conditions. The measurement was performed with a two-component laser-doppler-velocimeter (LDV) and a three-component stereoscopic particle-image-velocimeter (3C-PIV). Unsteady velocity data were obtained in axis perpendicular planes (LDV) and tangential planes (3C-PIV) between stator and rotor as well as downstream of the rotor. The results of the time-resolved investigation at several radii show the vortex shedding process from the trailing edges of nozzle guide vanes and rotor blades. This vortex shedding was found to be phase locked to higher harmonics of the blade passing frequency. Pressure waves evoked by reflection of the trailing edge shocks of the vanes on the passing rotor blades interact with the boundary layers on the rear suction side of the vanes and on the rotor blade surfaces while running upstream and downstream the flow. They are responsible for this phase-locking phenomenon of the shedding vortices. At midspan, the vortices shedding from stator and rotor blades were also observed by PIV. The in-plane vorticity distribution was used to discuss the wake-wake interaction indicating that wake segments from the nozzle guide vanes were chopped by the rotor blades. These chopped segments are still visible in the distributions as a pair of counter rotating vortices. The nozzle wake segments are transported through the rotor passages by the flow, influencing the vortex street of the rotor blades as they pass by with the higher velocity of the main flow. A comparison with a numerical simulation is also given.
Existence of radial solutions for the $p$-Laplacian elliptic equations with weights

Using the definition of solution and the qualitative properties established in the recent paper [17], some existence results are obtained both for crossing radial solutions and for positive or compactly supported radial ground states in $\mathbb R^n$ of quasilinear singular or degenerate elliptic equations with weights and with non--linearities which can be possibly singular at $x=0$ and $u=0$, respectively. The technique used is based on the papers [1] and [12]. Furthermore we obtain a non--existence theorem for radial ground states using a technique of Ni and Serrin [13].
Ultra-high transmittance through nanostructure-coated glass for solar cell applications

Ultra-high, broadband transmittance through coated glass windows is demonstrated over a wide range of incident angles. Near perfect 100% transmittance through a glass substrate has been achieved over select spectral bands, and the average transmittance increased to over 97% for photons incident between 0° and 75° with wavelengths between 400 nm and 1600 nm. The measured improvements in transmittance result from coating the windows with a new class of materials consisting of porous SiO2 nanorods.
Canonical forms and principal systems for general disconjugate equations

It is shown that the disconjugate equation (1) Lx = (1/,,)(d/dt) (l//,) **. (d/dt)(l//A)(d/dt)(x/,lo) = 0, a 0, and (2) A, Ee C(a,b), can be written in essentially unique canonical forms so that fb /,dt = X0 (fa Jidt = 00) for 1 < i < n 1. From this it follows easily that (1) has solutions xi, . , x. which are positive in (a, b) near b(a) and satisfy lim,. b-xi(t)/xj(t) = (lim,.ax&(t)/xj(t) = oo) for 1 ? i < j < n. Necessary and sufficient conditions are given for (1) to have solutions yl, . ,y,, such that lim, . b-y,(t)/yJ(t) = lim,. a+yj(t)/yi(t) = 0 for 1 < i <j < n. Using different methods, P. Hartman, A. Yu. Levin and D. Willett have investigated the existence of fundamental systems for (1) with these properties under assumptions which imply the stronger condition (2') A3, E C(-)(a, b).
The relationship between the solutions of the parabolic equation method and first Rytov approximation in stochastic wave propagation theory

The source of the curious exact agreement between the predictions of the disparate approaches of weak and strong fluctuation theory for the mutual coherence functions of plane and spherical wave propagation is identified. It is found that the linear approximation of the Ricatti equation that results within the Rytov method reduces to the parabolic equation of strong fluctuation theory only for the plane and spherical wave cases. Such a reduction does not prevail for the general beam wave case.
Traditional Galleries Require Fewer Watchmen

Chvatal’s watchman theorem shows if the walls of an art gallery form an n-sided polygon then at most $[ n /3 ]$ watchmen are needed to guard it, and that this number is best possible. In this paper it is shown that if every pair of adjacent sides of the polygon form a right angle then at most $[ n / 4 ]$ guards are needed, and again this result is best possible. Our proof depends on showing that any finite region bounded by a finite number of edges, each of which lies parallel to one of a fixed pair of perpendicular axes, has a partition into convex quadrilaterals.
Photoelectron excitation of N2 in the day airglow

The intensity of the 3371 A (0, 0) band of the N2 second positive system and the energy spectrum and flux of daytime photoelectrons were measured simultaneously between the altitudes of 100 and 300 km with instruments aboard a Nike-Tomahawk rocket. A zenith intensity of 230 rayleighs above 120 km was observed, and a maximum volume emission rate of 25 photons sec−1 cm−3 was found to occur near 155 km. The altitude profile calculated by using the measured electron flux and the known excitation cross section for the C³Πu state gives an excellent fit to the photometer data. A study of the electron excitation of the first positive bands of N2 predicts a dayglow intensity of the (1, 0) band that is in good agreement with a recent observation.
Theory for normal state critical Kapitza resistance of 4He

We study a steady state, bearing a heat current, Q0. In the normal state of liquid 4He with constraining geometry, near the lambda point, at temperatures T greater than the lambda temperature, Tλ. Critical order parameter fluctuations near the boundary are incorporated in the expression for the non-local thermal resistivity. The Kapitza resistance is manifested by the additional temperature rise at the boundary, as compared with the bulk-extrapolated value. Sensitivity of the calculations to the application of the Dirichlet boundary condition is discussed.
Exterior stationary Navier‐Stokes flows in 3D with non‐zero velocity at infinity: approximation by flows in bounded domains

We consider stationary incompressible Navier‐Stokes flows in an exterior domain ℝ3\$ \bar \Omega $, where Ω ⊂ ℝ3 is bounded and open. Under the assumption that the velocity at infinity is non‐zero, we present a variational problem in BR\$ \bar \Omega $ such that a solution of this variational problem approximates the given exterior flow. The error associated with this approximation is estimated in terms of R, among other quantities. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)