Miracle-dz/UniFAR-FTUs huggingface dataset:
Arrested shear dispersion and other models of anomalous diffusion

The macroscopic dispersion of tracer in microscopically disordered fluid flow can ultimately, at large times, be described by an advection-diffusion equation. But before this asymptotic regime is reached there is an intermediate regime in which first and second spatial moments of the distribution are proportional to tν. Conventional advection-diffusion (which applies at large times) has ν = 1 but in the intermediate regime ν < 1. This phenomenon is referred to as ‘anomalous diffusion’ and this article discusses the special case ν = ½ in detail. This particular value of ν results from tracer dispersion in a central pipe with many stagnant side branches leading away from it. The tracer is “held up” or ‘arrested’ when it wanders into the side branches and so the dispersion in the central duct is more gradual than in conventional advection-diffusion (i.e. ν = ½ < 1). This particular example serves as an entry point into a more general class of models which describe tracer arrest in closed pockets of recirculation, permeable particles, etc. with an integro-differential equation. In this view tracer is arrested and detained at a particular site for a random period. A quantity of fundamental importance in formulating a continuum model of this interrupted random walk is the distribution of stopping times at a site. Distributions with slowly decaying tails (long sojourns) produce anomalous diffusion while the conventional model results from distributions with short tails.
Perpendicular anisotropy dependence of oscillatory interlayer coupling behavior in [Pt/Co]5/Ru/[Co/Pt]5 multilayers

The experiments on the [t1Pt/0.4Co]5/(0.2–5.0)Ru/[0.4Co/t2Pt]5 (thickness unit is nm) multilayers with perpendicular anisotropy (PA) indicate that the interlayer coupling shows an antiferromagnetic (AF) and a ferromagnetic oscillatory behavior with the thickness of Ru spacer layers from 0 to 5.0 nm, and that the AF oscillations display a superposition of two different periods, which are 0.8 and 1.1 nm, respectively. Moreover, we found that the magnitude of AF coupling strength J is closely related to the magnitude of PA caused by varied thickness of nonmagnetic Pt layer. Our experimental results can be explained by Bruno’s electron-optics model.
A computer-assisted proof of universality for area-preserving maps

I. Analysis of doubling: Feigenbaum universality for area-preserving maps Generating functions Further reduction of the problem Spectral properties Constructions of the operator $L$ Construction of the doubling operator II. Functional analysis on the computer: Interval and neighborhood arithmetics Spectral theory Interval and neighborhood arithmetics on a computer List of correspondences III. Proofs: Computer program Program output Table 1.
Solution of piecewise constant delay systems using hybrid of block‐pulse and Chebyshev polynomials

An efficient numerical method for finding the solution of piecewise constant delay systems is presented. The method is based upon hybrid of block‐pulse functions and Chebyshev polynomials. The operational matrix of delay is constructed. The properties of hybrid functions together with the operational matrices of integration, delay and product are used to convert the delay differential equation to an algebraic equation, thus greatly simplifying the problem. The method is easy to implement and yields very accurate results. The validity and applicability of the proposed method are demonstrated by considering different types of delay systems. Copyright © 2010 John Wiley & Sons, Ltd.
Maximum Likelihood Methods for Linear Models

This article presents a model that is a natural generalization of both the spatial effects linear model and the linear model with spatial disturbances. Maximum likelihood methods are presented that provide estimates of the parameters of the model together with the asymptotic variance-covariance matrix of the estimates. Numerical illustrations of these methods are provided.
Energy transfer in biphasic magnetised interstellar medium

The transfer of energy from large scales to smaller scales is investigated within the context of the neutral atomic phases of the interstellar medium threaded by a magnetic field. More precisely, we derive the reflection and transmission coefficients for linear transverse hydromagnetic waves incident normally on a cloud in slab geometry. Then, we obtain various interesting physical quantities such as the energy density transferred into the cloud. The results obtained differ from those given previously in the literature. We show in particular that the transfer of energy is efficient enough so that ( i ) the induced internal motions are of the same order of magnitude than the bulk motion of the clouds and ( ii ) the internal energy density provides significative additional non-thermal support for cloud stability, reaching the same order of magnitude than support by the static magnetic field. Finally, the case of molecular clouds is also briefly considered for which similar results are obtained.
Detection of the Carbon Chain Negative Ion C8H– in TMC-1

The negative molecular ion C8H- has been detected in the Galactic molecular source TMC-1. Four rotational transitions have been observed in the centimeter-wave band with the NRAO 100 m Green Bank Telescope (GBT) at precisely the frequencies calculated from the recent laboratory spectroscopy of this large carbon chain anion. C8H- is about 5% as abundant as C8H, or somewhat more than C6H- relative to C6H (1.6%). Improved values of the column densities of C6H- and C6H, and an upper limit for the abundance of the smaller carbon chain C4H- of 0.014% with respect to C4H, have also been determined.
The Weather and Circulation of February 1969

1. UNUSUAL WEATHER This last month of winter produced or prolonged some of the season's worst weather. The most notable weather seemed to be directly related to widespread blocking, including the continued heavy precipitation in California. Some unusual mean weather records and monthly totals are shown in table 1. Rain and snow created new February records in the West; in New England several alltime snow records were established. The other extreme , lack of precipitation, caused record monthly dryness in Michigan and Wisconsin. This was the sunniest February of record at Sault Ste. The addition of more snow in the upper Mississippi Valley, Utah, and the Sierra Nevada Mountains increased the threat of spring flooding and resulted in early warnings in some areas. Strong blocking continued to dominate the 700-mb circulation over the United States and Canada this month. Other areas affected by blocking include the North Atlantic , Europe, and most of Asia. Some degree of high-latitude blocking occurred each month since the summer of 1968 in the Northern Hemisphere and over North America since September 1968. Figure 1 shows the mean 700-mb circulation and figure 2 the mean 700-mb height anomaly for February 1969. The Aleutian Low was divided with one center over the Sea of Okhotsk and another cent,er in the Bering Sea. This occurred with the return of strong westerlies and a predominantly zonal flow in the western and central Pacific. In January the Aleutian Low was in the Sea of Okhotsk, and a strong ridge of more than 150 m above normal was over Alaska. From January to February, height anomaly changes (fig. 3) decreased by as much as 250 m near Kodiak Island. The 700-mb Low that was north of Hawaii last month was replaced by a ridge in February as anomalous heights increased. by more than 100 m. This Low and the associated abnormal cyclonic activity moved eastward into the trough already along t,he west coast of North America. This trough was then more than 100 m below normal, the deepest relative to normal in the Northern Hemisphere this month. Heavy precipitation in the West Coast States resulted from this deep trough with 2 in. or more each week of February. This trough also contributed to ridging
Post-AGB Stars

▪ Abstract In this contribution, a review is presented on the ample data obtained on post-AGB stars, both on the central stars and their circumstellar material. The fast evolutionary phase is characterized by a rapid change in the properties of the objects, but the variety is so large that there is yet no clear consensus on how the detailed studies of individual objects are linked together by evolutionary channels. The absence of strong molecular veiling in the photospheres of the central stars, together with a spread in intrinsic metallicity make post-AGB stars very useful in constraining AGB chemical evolutionary models. We discuss the surprisingly wide variety of chemical signatures observed. The onset in the creation process of the panoply of structures and shapes observed in planetary nebulae occurs during the short post-AGB evolution, but the physical nature of the processes involved is still badly understood. In the rapidly growing field of circumstellar mineralogy, post-AGB stars have their story .
Heat Transfer Measurements in a First-Stage Nozzle Cascade Having Endwall Contouring: Misalignment and Leakage Studies

This work supports new gas turbine designs for improved performance by evaluating endwall heat transfer rates in a cascade that is representative of a first-stage stator passage and incorporates endwall assembly features and leakage. Assembly features, such as gaps in the endwall and misalignment of those gaps, disrupt the endwall boundary layer, typically leading to enhanced heat transfer rates. Leakage flows through such gaps within the passage can also affect endwall boundary layers and may induce additional secondary flows and vortex structures in the passage near the endwall. The present paper documents leakage flow and misalignment effects on the endwall heat transfer coefficients within a passage which has one axially contoured and one straight endwall. In particular, features associated with the combustor-to-turbine transition piece and the assembly joint on the vane platform are addressed.
Molecular Dynamics Simulation of Strontium Titanate

The molecular dynamics method is used to simulate the thermophysical properties of SrTiO3 thermoelectric material in the temperature range 300–2200 K. The Morse-type potential functions added to the Busing–Ida type potential for interatomic interaction are used in the simulation. The interatomic potential parameters are determined by fitting to the experimental data of lattice parameters with temperature and the data reported in literature. The linear thermal expansion coefficient, heat capacity and lattice contributions to the thermal conductivity are analyzed. The results agree with the data reported in the literature.
Development and calibration of self-centring probes for assessing geometrical errors of machines

A new type of probe for calibration, verification or interim checking of machine tools as well as robots or parallel-kinematics machine tools is presented in this paper. This probe is part of a ball-artefact-based method to assess the geometrical errors of linear and angular axes in a quick and reliable way. The discussion about the best design concept for the self-centring probe, the mathematical modelling and design process of one of those concepts and the development of three different prototypes are shown. Different sensors and design options were developed to optimize the size and cost of the probe. The calibration of the probe prototypes by way of a kinematically coupled reference device to allow on-machine tests is shown. The uncertainties obtained were around 1 µm for one of the prototypes and below 5 µm for the other two. Finally, results of a geometrical verification of a machine tool are demonstrated, with values similar to the ones achieved using other methods, such as laser interferometry. Compared to those other methods, the new technique was shown to be less time consuming.
Zitterbewegung in quantum field theory

Traditionally, the zitterbewegung (ZB) of the Dirac electron has just been studied at the level of quantum mechanics. Seeing the fact that an old interest in ZB has recently been rekindled by the investigations on spintronic, graphene, and superconducting systems, etc., this paper presents a quantum-field-theory investigation on ZB and obtains the conclusion that, the ZB of an electron arises from the influence of virtual electron-positron pairs (or vacuum fluctuations) on the electron.
On the role of the Kelvin wave in the westerly phase of the semiannual zonal wind oscillation

Abstract The role of the Kelvin wave, discovered by Hirota (1978), in producing the westerly accelerations of the semiannual zonal wind oscillation in the tropical upper stratosphere is examined quantitatively. It is shown that, for reasonable values of the wave parameters, this Kelvin wave could indeed give rise to the observed accelerations. For the thermal damping rates of Dickinson (1973), the most likely range of phase speeds for a wavenumber 1 disturbance is from 45 to 60 m s−1. For “photochemically accelerated” damping rates (Blake and Lindzen, 1973), a phase speed in excess of 70 m s−1 would he required. The possibility of a significant modulation of the semiannual westerlies by the quasi-biennial oscillation is also suggested.
Energy equation formulations for two-temperature modelling of ‘thermal’ plasmas

Based on an equilibrium fluid model, built from the commercial Fluent software previously validated for thermal plasma characterizations on several geometries, a non-equilibrium two-temperature model was developed. This kind of model needs the use of two energy equations: one for the electrons, and the other for heavy particles. Nevertheless, depending on the authors, divergences exist in the expressions of equations. The main differences are related to the attribution of the ionization term and to the components of thermal conductivity in the energy equations. The two-temperature model developed is applied in a transferred arc configuration where the medium is described using the different formulations for the energy equations. The right formulation, based on the Boltzmann equation, is then applied in a transferred arc configuration for two values of current intensity of 100 and 600 A. We show that in order to obtain coherent and physical results in all the cases, special attention needs to be given: the ionization term, the reactive thermal conductivity and the radiation line contribution need to be considered in electron energy equations, whereas the reactive thermal conductivity due to dissociations and the continuum radiation contributions need to be associated with the heavy energy equations.
On nonlinear model equations for the response of premixed flames to acoustic like accelerations

The response of a dynamical flame model to imposed acoustic accelerations is studied analytically and numerically. Through linear stability analyses, two analytical approximations for the primary and the parametric stability boundaries are found. The approximation for the primary instability boundary is accurate for any periodic accelerations, in the limit of large acoustic frequencies. The critical acoustic amplitude u a for Landau–Darrieus instability suppression is identified and found to depend only on the density contrast and the shape of the periodic acoustic stimuli. The proposed model evolution equation is next integrated numerically with various imposed acoustic accelerations; the primary and parametric flame responses are identified. It is shown analytically and numerically that in the presence of a fully developed, yet weakened by acoustics, Landau–Darrieus (or primary) instability the wrinkle amplitude and the mean flame speed oscillate at the same frequency as the acoustic stimuli; the threshold for suppression of primary instability by acoustic forcing is determined exactly. Increasing the acoustic amplitude allows the flame to respond parametrically to the acoustics. This response is characterised by troughs and crests interchanging their roles while the mean flame speed again oscillates with the same frequency as the acoustic stimuli and at twice that of wrinkle amplitude oscillations.
Direct numerical simulation and analysis of instability enhancing parameters in liquid sheets at moderate Reynolds numbers

Direct numerical simulations based on the volume-of-fluid method have been performed in order to identify the influence of the inflow velocity conditions on the sensitivity of primary breakup phenomena. A liquid sheet ejected into a gaseous environment at moderate Reynolds numbers ranging from Re=3000 to 7000 was considered. The numerical setup allows to vary the influencing parameters individually such that numerical simulations can be performed as “numerical experiments” by varying each of the possible parameters separately. The focus of the present study was directed to the identification of those parameters that most strongly enhance primary breakup phenomena. These key parameters are the flow quantities such as the range of the inflow velocity and the inherent character of the mean velocity profile as well as the corresponding dimensionless groups and turbulence quantities of the nozzle flow. The present results show that in addition to these well known quantities the kinetic energy flux, which depen.
Associations between tropical cyclone activity in the Southwest Indian Ocean and El Niño Southern Oscillation

The link between El Niño Southern Oscillation (ENSO) and tropical cyclone activity over the Southwest Indian Ocean [(0°–30°S) × (48°–90°E)] is revisited. Based on the records for 1981–2013, we show that cyclonic activity decreases dramatically during strong ENSO events: only a few cases are observed during the January‐March period. This pattern is attributed to changes in large‐scale thermodynamic parameters. Although El Niño is correlated with an increase in tropospheric moisture and sea‐surface temperatures, it is also associated with an equatorward shift of the subtropical jet. When El Niño is sufficiently strong, the latter effect may dominate the former, inhibiting tropical cyclone activity.
Abundance stratification and pulsation in the atmosphere of the roAp star $\boldmath\gamma$ Equulei

We present the evidence for abundance stratication in the atmosphere of the rapidly oscillating Ap star Equ. Ca, Cr, Fe, Ba, Si, Na seem to be overabundant in deeper atmospheric layers, but normal to underabundant in the upper layers with a transition in the typical line forming region of 1:5 < log5000 < 0:5. This stratication prole agrees well with diusion theory for Ca and Cr, developed for cool magnetic stars with a weak mass loss of 2:5 10 15 M yr 1 . Pr and Nd from the rare earth elements have an opposite prole. Their abundance is more than 6 dex higher above log5000 8:0 than in the deeper atmospheric layers. We further discuss the implications of abundance stratication in the context of radial velocity amplitudes and phases observed by Kochukhov & Ryabchikova (2001) for a variety of spectral lines and elements using high spectral and time resolved, high S/N observations.
An approximation for the on‐axis field of an elliptical piston transducer

An approximate analytic formula is given for the on‐axis pressure of a baffled, elliptically shaped piston transducer. This approximate formula results from truncating an exact series expansion for the integral that determines the on‐axis pressure. The reported formula is considerably more accurate than the previous expression. The accuracy and range of validity of the new result are determined by comparison with a numerical evaluation of the relevant integral.
Investigating the use of an adjustment task to set preferred colour of ambient illumination

An experiment was carried out to examine the method of adjustment when determining user preferences for the colour appearance of ambient lighting. A booth was lit using luminaires containing an array of white and coloured light emitting diodes (LEDs), allowing continuous variation of correlated colour temperature (CCT) between 2736 and 4014 K. It was predicted that the preferred CCT would be influenced by the available stimulus range, the anchor (initial setting before adjustment), adaptation time before onset of adjustment action and type of control dial. Preference was estimated for three different CCT stimulus ranges within the available range. All three ranges led to significantly different results for preferred CCT: 3288, 3490 and 3671 K. The experimental results confirmed that stimulus range, anchor and adaptation time have significant effect on the preferred CCT determined using the adjustment task, and thus, the importance of considering and reporting this information in studies that employ the method of adjustment. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2013
Sequential Design for Ranking Response Surfaces

We propose and analyze sequential design methods for the problem of ranking several response surfaces. Namely, given $L \ge 2$ response surfaces over a continuous input space $\cal X$, the aim is to efficiently find the index of the minimal response across the entire $\cal X$. The response surfaces are not known and have to be noisily sampled one-at-a-time. This setting is motivated by stochastic control applications and requires joint experimental design both in space and response-index dimensions. To generate sequential design heuristics we investigate stepwise uncertainty reduction approaches, as well as sampling based on posterior classification complexity. We also make connections between our continuous-input formulation and the discrete framework of pure regret in multi-armed bandits. To model the response surfaces we utilize kriging surrogates. Several numerical examples using both synthetic data and an epidemics control problem are provided to illustrate our approach and the efficacy of respective adaptive designs.
Strain relaxation in AlGaN multilayer structures by inclined dislocations

To examine further the strain relaxation produced by inclined threading dislocations in AlGaN, a heterostructure with three AlGaN layers having successively increasing Ga contents and compressive strains was grown on an AlN template layer by metalorganic vapor-phase epitaxy. The strain state of the layers was determined by x-ray diffraction (XRD) and the dislocation microstructure was characterized with transmission electron microscopy (TEM). As the GaN mole fraction of the heterostructure increased from 0.15 to 0.48, the increased epitaxial strain produced inclined dislocations with successively greater bend angles. Using the observed bend angles, which ranged from 6.7° to 17.8°, the measured strain relaxation within each layer was modeled and found to be accounted for by threading-dislocation densities of 6–7×109/cm2, in reasonable agreement with densities determined by TEM and XRD. In addition to the influence of lattice-mismatch strain on the average bend angle, we found evidence that local strain inh.
Thermal stability of graded exchange spring media under the influence of external fields

The thermal stability of graded exchange spring media for perpendicular recording is investigated. It is found that the energy barrier linearly decreases with the external field strength. This leads to a high thermal stability in the low frequency recording limit, where large demagnetizing fields act on the media. The attempt frequency of graded media is about a factor of 5 larger than the attempt frequency of comparable single phase media.
Equivalence theorem and Faddeev-Popov ghosts

An algebraic proof of the equivalence theorem, to all orders of perturbation theory, is obtained by applying the equations of motion repeatedly in a normal-product algorithm. It is shown that, for certain nonlocal transformations, the equivalence theorem can be maintained by introducing Faddeev-Popov ghosts. (AIP)