Miracle-dz/UniFAR-FTUs huggingface dataset:
Relaminarization in highly favourable pressure gradients on a convex surface

We report here the results of experiments on two flows – one on a convex surface and the other on a flat surface – designed to bring out explicitly the influence of streamwise curvature on relaminarization in highly favourable pressure gradients. In both flows, the initial conditions and the streamwise distribution of the Launder pressure-gradient parameter $K$ are virtually identical. The maximum value of $K$ is $6.2\,{\times}\, 10^{-6}$, well above the critical value of about $3.5\,{\times}\, 10^{-6}$ usually advocated for relaminarization. The spatial extent of the acceleration zone is of order 10 initial boundary-layer thicknesses, appreciably shorter than in earlier work in order better to simulate conditions at the leading edge of a typical aircraft wing. The fall in skin friction coefficient is steeper and the rise in shape factor sharper on the convex surface than on the flat surface, indicating that relaminarization on the convex surface is both more rapid and more nearly complete. In the crucial relaminarizing zone, two-layer quasi-laminar theory is found to predict the convex-surface mean-flow parameters more accurately than the flat-surface flow, without any explicit modelling of curvature effects. Thus, experimental results and supporting calculations both indicate that the dominant effect of streamwise convex curvature on the mean flow is to promote more rapid and complete relaminarization in an accelerated turbulent boundary layer, thus enhancing the probability of its occurrence on the leading edge of swept wings where both factors are significantly in operation.
Analyticity of the nonlinear scattering operator

We present a new and simpler proof that the nonlinear scattering operator $\S$ is analytic on energy space. We apply it in particular to a fourth-order nonlinear wave equation in Rn. In addition, we prove that $\S$ determines the scatterer uniquely and that for small powers there is no scattering.
The Luminosity Function of OB Associations in the Galaxy

OB associations ionize the interstellar medium, producing both localized H II regions and diffuse ionized gas. The supernovae resulting from these associations pressurize and stir the interstellar medium. Using Smith, Biermann, & Mezger's compilation of radio H II regions in the Galaxy, and Kennicutt, Edgar, & Hodge's optical study of H II regions in nearby galaxies, we show that the luminosity distribution of giant OB associations in the Galaxy can be fit by a truncated power law of the form 𝒩a(>S)=𝒩au[(Su/S)-1], where S is the ionizing photon luminosity, 𝒩a(>S) is the number of associations with a luminosity of at least S, and Su is the upper limit to the distribution. The coefficient 𝒩au is the number of the most luminous associations, with a luminosity between 0.5Su and Su. For the Galaxy, 𝒩au=6.1; the fact that the number of the most luminous associations is significantly larger than unity indicates that there is a physical limit to the maximum size of H II regions in the Galaxy. To extend the luminosity distribution to small H II regions, we assume that the birthrate of associations, a(>𝒩*), is also a truncated power law, a(>𝒩*)∝[(𝒩*u/𝒩*)-1], where 𝒩* is the number of stars in the association. For large associations, the ionizing luminosity is proportional to the number of stars, S∝𝒩*; for smaller associations, we use both an analytic and a Monte Carlo approach to find the resulting luminosity distribution 𝒩a(>S). H II regions are generally centrally concentrated, with only the dense central regions being bright enough to appear in radio catalogs. Anantharamaiah postulated that radio H II regions have extended envelopes in order to account for diffuse radio recombination line emission in the Galaxy. Some of these envelopes are visible as the ionized “worms” discussed by Heiles and coworkers. We estimate that on the average the envelopes of radio H II regions absorb about twice as many ionizing photons as the radio H II regions themselves. Allowing for the ionizing radiation that is absorbed by dust (about 25% of the total), we find that the maximum ionizing photon luminosity of a Galactic OB association is Su ≃ 4.9 × 1051 photons s-1, corresponding to an Hα luminosity of about 5 × 1039 ergs s-1. The total ionizing luminosity of this distribution of OB associations can account for the thermal radio emission and the N II far-infrared emission of the Galaxy. The number of massive stars in the associations is consistent with estimates of the rate of massive star supernovae in the Galaxy. Associations produce several generations of stars over their lifetimes, and the largest associations are predicted to produce about 7000 supernova progenitors. Fitting the surface density of associations to an exponential of the form d𝒩a(𝒩*)/dA∝ exp (-R/HR) with a scale length HR = 3.5 kpc gives a number of OB associations in the solar neighborhood that is consistent with observation. The H II envelopes contribute to pulsar dispersion measures and can account for the increased dispersion measure observed in the inner Galaxy.
Vertical Structure of Thunderstorm Outflows

Abstract Cold air outflow from thunderstorms has been observed from a multi-level 461 m tower in central Oklahoma. Four life-cycle stages are determined from 20 outflows sampled. Each outflow is affected by the behavior and character of the parent thunderstorm and by the flow and stratification in both the warm ambient air and the cold outflow air. This produces much variation from case to case and makes difficult the description of a representative outflow model. However, cases believed to depict each of the outflow stages are chosen and discussed in detail. The study is confined to the tower layer depth and concentrates on the characteristics of the outflow's leading edge. Outflow origin is not discussed. The leading edge of the outflow is characterized by strong shears in horizontal and vertical winds. Updrafts, which occur in a 1.5 km wide band ahead of the outflow, often exceed 6 m s−1. Maximum low-level horizontal wind gusts are found to be directly related to the translational speed of the front. F.
Deep-level optical spectroscopy investigation of N-doped TiO2 films

N-doped TiO2 films were deposited on n+-GaN∕Al2O3 substrates by reactive magnetron sputtering and subsequently crystallized by annealing at 550 °C in flowing N2 gas. The N-doping concentration was ∼8.8%, as determined from x-ray photoelectron spectroscopy measurements. Deep-level optical spectroscopy measurements revealed two characteristic deep levels located at ∼1.18 and ∼2.48eV below the conduction band. The 1.18 eV level is probably attributable to the O vacancy state and can be active as an efficient generation-recombination center. Additionally, the 2.48 eV band is newly introduced by the N doping and contributes to band-gap narrowing by mixing with the O2p valence band.
Attendance and attainment in a Calculus course

In this paper the relationship between attendance and attainment in a standard calculus course is investigated. Calculus could in principle be studied without attending lectures due to the wealth of material available (in hardcopy and online). However, in this study we will show that the pass rate of students attending classes regularly (>75% of the classes) is much higher than the pass rate of students attending fewer classes. We use a logistic model to investigate whether this correlation is significant. We will argue why we believe that this correlation between attendance and attainment is causal, i.e. why it is necessary for most students to attend classes in order to (improve their chances to) pass the exam.
More efficient monte carlo methods obtained by using ranked set simulated samples

Estimation of integrals by crude Monte Carlo methods, using uniform simulated sample (USS) required a large sample size to achieve high accuracy. Reduction in sample size is achieved using USS with the sophisticated Monte Carlo methods such as antithetic, importance or control variate sampling. In this paper, we show that the performance of these methods is substantially improved by using ranked simulated samples (RSIS) in place of USS. This results in a very large saving in of simulated sample size and hence in cost and time. We show that the modified methods using RSIS provide unbiased estimators for the integrals. Some characteristics and theoretical concepts of RSIS are given. A simulation study is conducted to compare the performance of the methods using RSIS to USS.
General Relativistic Effects on the Infrared Spectrum of Thin Accretion Disks in Active Galactic Nuclei: Application to Sagittarius A*

The possibility that some portion of the infrared (IR) radiation emanating from active galactic nuclei (AGNs) may arise from disklike structures of ionized plasma accreting onto massive black holes motivates the investigation of the effects of strong gravitational fields in the vicinity of emitting particles on the observed radiation. Numerous previous studies have been incomplete in several respects: (1) they have neglected to take into account the observed specific power flux contribution of radiation emitted from the underside of the disk and gravitationally lensed into the upper half-hemisphere, (2) they have considered only a limited range of observing positions and hole spins, and (3) many have been restricted to examination of the steady state flux arising from homogeneous disks. The present study develops, within the context of the optically thick, geometrically thin accretion disk model, a set of new calculational techniques based on an analysis of the algebraic properties of the effective potential functions governing photon propagation in the Kerr metric; ancillary techniques, such as that of “extended images,” are introduced and employed to illustrate aspects of general relativistic image formation that affect the observed time-dependent flux arising from a thermally inhomogeneous accretion disk. The contribution of the first-orbit disk images, including the effects of disk self-blocking, to the observed flux are fully taken into account for the entire range of observing positions and hole spins for both the steady state and time-dependent cases. The procedure is illustrated by application of the results to the paradigm case of the Galactic center black hole candidate Sagittarius A*. Current observations are somewhat contaminated because of poor angular resolution, making this exercise still only an illustrative examination of the method. However, the future deployment of the Near-Infrared Camera and Multiobject Spectrometer (NICMOS) on HST should provide data with sufficient sensitivity for direct comparison with our calculated K-band fluxes and light curves. Of particular interest in this comparison is the expected reversal of the disk's angular momentum in Sgr A* on a timescale of 10 yr or so. We discuss the distinct spectral signature of a retrograde disk versus that of a prograde configuration and demonstrate the feasibility of observing this transition.
Measurements of the fast-ion distribution function at ASDEX upgrade by collective Thomson scattering (CTS) using active and passive views

Collective Thomson scattering (CTS) can provide measurements of the confined fast-ion distribution function resolved in space, time and 1D velocity space. On ASDEX Upgrade, the measured spectra include an additional signal which previously has hampered data interpretation. A new set-up using two independent heterodyne receiver systems enables subtraction of the additional part from the total spectrum, revealing the resulting CTS spectrum. Here we present CTS measurements from the plasma centre obtained in L-mode and H-mode plasmas with and without neutral beam injection (NBI). For the first time, the measured spectra agree quantitatively with the synthetic spectra in periods with and without NBI heating. For the discharges investigated, the central velocity distribution of neutral beam ions can be described by classical slowing down. These results will have a major impact on ITER physics exploration, since CTS is presently the only diagnostic to measure the confined alpha particles produced by the fusion reactions.
On the analysis of band 3 of the ISO-SWS calibration sources

We analyse ISO–SWS 01 ($R \sim 1500$) $12{-}27.5\,\mu$m (band 3) spectra of the 10 standard calibration stars with the highest flux using synthetic spectra generated from (marcs) atmosphere models. The comparison between the observed and synthetic spectra reveals the quality of (1) the atmospheric model construction and subsequent synthetic spectra computation and of (2) the (OLP 10.1) calibration and data reduction of the spectrometer at these wavelengths. The models represent the general features of the observations, but the synthetic spectrum computation is hampered by the lack of comprehensive molecular and atomic line lists. We also suspect some problems with the temperature distribution in the outer layers of the model and inaccuracies in the extrapolation of the collision-induced absorption coefficients of H 2 pairs. We detect baseline ripples and fringes in the observed spectra, that survive the calibration and detailed reduction process. Photometric calibration uncertainties are estimated by means of the scaling factors between the synthetic and observed spectra.
Computation of Hypersonic Shock Waves in Diatomic Gases Using the Generalized Boltzmann Equation

The paper describes the methodology for computing hypersonic non‐equilibrium shock wave flows of diatomic gases using the Generalized Boltzmann Equation (GBE) including both the vibrational—translational (VT) and rotational—translational (RT) relaxations. For the VT relaxation, GBE is always solved. For the RT relaxation, two approaches are employed. In the first approach, for the RT relaxation GBE is solved. This approach is computationally very intensive since it requires solving the complete GBE for both vibrational and rotational degrees of freedom. In the second approach, a two‐level BGK type model of RT relaxation is employed. The second approach is much more efficient than the first (about 20 times faster). The paper describes the two‐level RT relaxation model. The model is validated by computing the shock structure at high Mach numbers by comparing the results with the complete GBE solution. Computations are then performed for the shock structure accounting for both the vibrational and rotational .
On Flows in Stochastic Marked Graphs

In this work, the discrete event systems called Stochastic Marked Graphs (SMGs) are investigated from a stability point of view. Being a special class of Timed Petri Nets with stochastic firing times, they are studied under general assumptions of stationarity and ergodicity of the firing times and ergodicity of flows of their free strongly connected components. The values of the flows of tokens in an SMG are specified as functions of the intrinsic rates of its free strongly connected components, and various stability issues are discussed.
Thermal and petrological consequences of melt migration within mantle plumes

The high temperatures and high degrees of melting expected in the core of mantle plumes have virtually no expression in the eruption temperatures of hotspot lavas, nor in the composition of their glasses, which is restricted in the basaltic field. A solution to this paradox is looked for in the melt migration processes within the melting region of mantle plumes. Three dimensional convective calculations at Rayleigh number of 106 allow estimates of the possible temperature, melt fraction and stress fields within a plume. Two regions with different melt migration patterns can be distinguished. A lower zone ranging in depth from the base of the melting region (150 km) to around 80—100 km where the first melt fraction is redistributed in a sub-horizontal vein network and convects in response to the steep horizontal temperature gradient. This process is able to homogenize the temperature within the melting region very efficiently. The high (300 °C) temperature contrast between the centre of the plume and the surrounding mantle can be reduced to a few tens of degrees at the top of this zone. Fractional crystallization of high pressure phases will strongly modify the composition of the melt as it circulates toward the periphery of the melting region. A second upper zone, where the sub-vertical vein orientation will make possible rapid melt migration toward the surface, extends to the base of the lithosphere. Due to the buffering of the plume temperature around a value close to the mean upper mantle temperature, the degree of adiabatic melting within this upper zone will not greatly exceed that beneath normal spreading centres, even in the case of on-ridge hotspots. The lavas erupted at hotspots are likely to result from the mixing in various proportions of these low pressure melts (basalts) with the highly evolved liquids (possibly with kimberlitic to alkalic affinities) resulting from fractional crystallization of the high-pressure melt fractions produced at the base of the melting region. This scenario could account for the low eruption temperatures and Mg contents of hotspot lavas, in spite of a complex high pressure, and thus high temperature, history evidenced by some geochemical trends.
On the Marcinkiewicz-Fejér means of double Fourier series with respect to the Walsh-Kaczmarz system

The main aim of this paper is to prove that the maximal operator of Marcinkiewicz-Fejer means of double Fourier series with respect to the Walsh-Kaczmarz system is bounded from the dyadic Hardy-Lorentz space H pq into Lorentz space L pq for every p > 2/3 and 0 < q ≦ ∞. As a consequence, we obtain the a.e. convergence of Marcinkiewicz-Fejer means of double Fourier series with respect to the Walsh-Kaczmarz system. That is, σ n ( f, x 1 , x 2 ) → ( x 1 , x 2 ) a.e. as n → ∞.
Variational assimilation of meteorological observations with the direct and adjoint shallow-water equations

Experiments of variational assimilation, similar to those already performed by the authors on a vorticity equation model are performed on a shallow-water equation model. The variational algorithm requires the computation of the gradient of the distance function to be minimized with respect to the model state at the beginning of the assimilation period. As in the previous experiments, this gradient is computed by using the adjoint equations of the model. Northern Hemisphere observations of wind and geopotential, distributed at the 500 mb level over a 24-h time period, are assimilated with a spectral model truncated at degree 21. The results confirm the results previously obtained, namely that the variational process reconstructs to a satisfactory degree of accuracy the meteorological structures of the flow. In addition: (i) Gravity wave noise can be efficiently eliminated by adding an appropriate penalty term to the distance function, and by introducing in the variational process a nonlinear normal mode initialization algorithm. The latter has the effect of improving the numerical conditioning of the variational process. (ii) The quality of forecasts produced from the results of variational assimilation is similar to the quality of shallow-water equation forecasts produced from the results of operational assimilations, which use many more data and more realistic models. Assimilations performed with a model truncated at degree 42 produce similar results. They also show that the numerical efficiency of the variational process, as measured by the number of descent steps necessary to reach convergence, is almost insensitive to the dimension of the model phase space. Finally, study of the variations of the distance function suggests that, as in the case of the vorticity equation, the tangent linear approximation to the model equations is valid in the conditions of data assimilation. DOI: 10.1034/j.1600-0870.1990. t01-4-00004.x
Modeling Reporting Delays and Reporting Corrections in Cancer Registry Data

The Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute is an authoritative source of cancer incidence statistics in the United States. The SEER program is a consortium of population-based cancer registries from different areas of the country. Each registry is charged with collecting data on all cancers that occur within its geographic area. As with any disease registry, there is a delay between the time that the disease (cancer) is first diagnosed and the time that it is reported to the registry. The SEER program has allowed for reporting delays of up to 19-months before releasing data for public use. Nevertheless, additional cases are discovered after the 19-month delay, and these cases are added in subsequent releases of the data. Further, any errors discovered are corrected in subsequent releases. Such reporting delays and corrections typically lead to underestimation of the cancer incidence rates in recent diagnosis years, making it difficult to monitor trends. In this article we study models that account for reporting delays and corrections in predicting eventual cancer counts for a diagnosis year from the preliminary counts. Previous models of this type have been studied, especially as applied to AIDS registries. We offer several additions to existing models. First, we explicitly model the reporting corrections. Second, we model the delay distribution with very general models, combining aspects of previous nonparametric-like models (i.e., models that have a separate parameter for each delay time) with more parametric models. Third, we allow random reporting-year effects in the model. Practical issues of model selection and how the data are classified are also discussed, particularly how the definition of a reporting correction may change depending on how subpopulations are defined. An example with SEER melanoma data is studied in detail.
Bin packing with discrete item sizes, part II: Tight bounds on First Fit

In the bin packing problem, a list L of n items is to be packed into a sequence of unit capacity bins with the goal of minimizing the number of bins used. First Fit (FF) is one of the most natural on-line algorithms for this problem, based on the simple rule that each successive item is packed into the first bin of the sequence that currently has room for it. We present an average-case analysis of FF in the discrete uniform model: The item sizes are drawn independently and uniformly at random from the set {1/k,…,(k - 1)/k}, for some k > 1. Let WFF(L) denote the wasted space in the FF packing of L, i.e., the total space still available in the occupied bins. We prove that , i.e., there exists a constant c > 0 such that for all n, k sufficiently large. By a complementary lower bound argument, we prove that this result is sharp, unless k is allowed to grow with n at a rate faster than n1/3 in which case E[WFF(L)] = θ(n2/3). Finally, we show that this last result carries over to the continuous uniform model, where item sizes are chosen uniformly from [0, 1]. The O(n2/3) upper bound for the continuous model is new and solves a problem posed a decade ago. The proofs of many of these results require extensions to the theory of stochastic planar matching. © 1997 John Wiley & Sons, Inc. Random Struct. Alg. , 10, 69–101 (1997)