Miracle-dz/UniFAR-FTUs huggingface dataset:
Homogeneous Turbulence in Bubbly Flows

The present study is devoted to the interaction between a swarm of bubbles and a turbulent field in a linear shear flow. The transversal and longitudinal evolutions of the void fraction and of the Reynolds stress tensor have been measured. When the air bubbles are blown uniformly into the shear, the void fraction profiles exhibit a strong gradient which can be explained by kinematical effects. No void migration has been observed. The behavior of the Reynolds tensor indicates that the nonisotropy induced by the mean velocity gradient decreases when the void fraction increases. A simple mechanism is proposed to interpret this fact, and a turbulence model based on one-point closures is compared to the experimental data.
High-pressure–high-temperature phase relations of Mg Ge O 3 : First-principles calculations

The high-pressure\char21{}high-temperature behavior of $\mathrm{Mg}\mathrm{Ge}{\mathrm{O}}_{3}$ has been investigated by first-principles computations. It is found that at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the first transformation from ilmenite to orthorhombic perovskite at $24\char21{}38\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ is followed by the second one to the $\mathrm{Ca}\mathrm{Ir}{\mathrm{O}}_{3}$ structure at $51\char21{}56\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. Quasiharmonic free energy calculations suggest that the first transformation has a negative Clapeyron slope ($\ensuremath{-}9.3\phantom{\rule{0.3em}{0ex}}\mathrm{MPa}∕\mathrm{K}$ at $1000\phantom{\rule{0.3em}{0ex}}\mathrm{K}$), whereas the second one has a less temperature-sensitive positive Clapeyron slope ($+7.8\phantom{\rule{0.3em}{0ex}}\mathrm{MPa}∕\mathrm{K}$ at $1000\phantom{\rule{0.3em}{0ex}}\mathrm{K}$). It is also confirmed that the $\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ structure does not have its own stability $P,T$ conditions. Pressure dependence of the Goldschmidt tolerance factor indicates a clear correlation between distortion of the perovskite structure and relative stability of perovskite and postperovskite structures.
Extreme Ultraviolet Explorer Observations of λ Andromedae

Extreme-ultraviolet spectra (70-740 Å) and light curves (75-175 Å) of the spectroscopic binary system λ Andromedae (HD 222107) were obtained with the Extreme Ultraviolet Explorer (EUVE) satellite in 1997 July and August. Two flares were detected during the observations that spanned 15 days, or almost of the orbital period of 20.5 days, with a total exposure time of 283 ks. The emission measure distribution (EMD) of λ And derived from a line-based analysis shows an increasing slope with temperatures over the range log Te (K) = 6.5-7.3 as well as a remarkable narrow enhancement or "bump" around log Te (K) = 6.9. Both flaring and quiescent EUVE spectra were obtained. During the flares, small changes were detected in both the general slope of the EMD and the height of the bump, but the bump remained very stable in its temperature. Electron densities of log Ne (cm-3) ~ 12.3 are indicated at temperatures of log Te (K) = 7 using Fe XXI and Fe XXII emission features, and those densities increase to log Ne (cm-3) ~ 12.9 during flaring episodes.
60 GHz monolithic LNA utilizing high-speed InAlAs/InGaAs/InP HEMTs and coplanar waveguides

A monolithic two-stage low noise amplifier (LNA) on InP substrate is presented. Coplanar waveguides and lumped elements are used for the matching and biasing networks. The circuit is fully passivated and contains common ports for the gate and the drain bias. The total chip size is 2 mm/spl times/1 mm. A gain of 15 dB and an input and output matching better than -8 dB were achieved at 60 GHz.
Fundamental Fraction Knowledge of Preservice Elementary Teachers: A Cross‐National Study in the United States and Taiwan

The purpose of this paper is to show the similarities as well as the differences of fundamental fraction knowledge owned by preservice elementary teachers from the United States (N= 89) and Taiwan (N= 85). To this end, we examined and compared their performance on an instrument including 15 multiple-choice test items. The items were categorized into four different types of fundamental fraction constructs, including part–whole relationship, quotient, equivalence, and meanings of operations. Each item was embedded in the area, linear, or set model except for the items constructed out of the meaning of operations. Several items were featured with a pictorial illustration. Quantitative analysis showed that U.S. preservice teachers were significantly outperformed by their Taiwanese counterparts overall. The difference between the two groups was statistically significant on 12 of 15 items. Findings suggest that preservice elementary teachers from both countries need to be better prepared in their understanding of the meaning of fraction multiplication or division operations. Findings also suggest that U.S. preservice elementary teachers need to be more knowledgeable in dealing with fraction problems embedded in a linear model. Further research is suggested to study the issues raised from the findings.
IUE spectra of the nuclei of M31 and M32

Observed spectra are reproduced in the 1000-3400 wavelength range; line identifications are tabulated, and spectrophotometry of parts of the continua is given. The flux density of a few line emissions can be estimated from their equivalent widths. The strongest line emissions differ in the two nuclei, and they do not fit spectral patterns that are observed in the sun, hot stars, gaseous nebulae, or quasi-stellar objects. However, the absorption-line features are rather similar to those of the sun.
Identifying sudden cardiac death risk and specifying its occurrence time by analyzing electrocardiograms in natural time

Sudden cardiac death (SCD) is a frequent cause of death and may occur even if the electrocardiogram seems to be similar to that of a healthy individual. A method which not only identifies the risk but also provides an estimate of the time of an impending cardiac arrest is proposed. Analyzing 159 electrocardiograms in natural time, the authors find that the key quantity is the entropy change under time reversal. After it becomes maximum at the scale of 13 heartbeats, ventricular fibrillation starts within ∼3h in 16 out of 18 SCDs. The method also distinguishes congestive heart failure patients from SCD.
Transfer properties of the large‐scale eddies and the general circulation of the atmosphere

The transfer of heat and momentum by motion on the scale of cyclone waves and long waves is deduced from a knowledge of their mechanics. The law of horizontal transfer of entropy is independent of notions of mixing but is similar to that for non-isotropic diffusion. The law accurately represents the annual variation of heat-flux in the Northern Hemisphere. Perturbation theory suggests realistic spatial variations for the transfer and provides a rational basis for calculating transfer coefficients which can then be used to find the flux of other conservative quantities. Most importantly the Equatorward flux of potential vorticity is well defined and is shown to determine the horizontal flux of momentum uv. The mean surface winds, and the mean meridional circulation (which is seen to be frictionally driven) are then determined. A model of the general circulation is defined by these properties, and this is integrated analytically for a simplified case and compared with motion observed in the Gulf Stream, the mesosphere, and dishpan experiments as well as the troposphere.
Near-Infrared Synthetic Images of Protostellar Disks and Envelopes

We present a grid of near-infrared (IR) synthetic images of pre-main-sequence stars at different stages of evolution, which we simulate by varying envelope mass, disk radius and mass, and outflow cavity shape. Our aim is to determine how variations in physical properties of young stellar objects (e.g., mass infall rate, disk size) affect their observed colors and morphology, and use this information to highlight observable differences between different evolutionary states. We show that the near-IR colors are a function of envelope mass infall rate and inclination; hence both parameters must be constrained if colors are to be used to infer a source's true evolutionary state. Sources with more opaque envelopes have redder diffuse colors, because the scattered light suffers reddening as it propagates through the envelope. Somewhat counterintuitively, colors are reddest at intermediate inclinations (i ~ 45°-70°) and then become bluer edge-on, where light is ~100% scattered. Thus a source with relatively blue colors could be an evolved source or a younger source oriented edge-on. Importantly, we find that at inclinations where scattered light dominates, it is erroneous to derive extinction AV from observed colors; fully half of all objects will underestimate AV by at least an order of magnitude. We use our models to interpret six protostellar sources in the Taurus-Auriga molecular cloud observed with HST NICMOS. Of the six young stellar objects modeled in this paper, five require an infalling envelope to match the colors and should thus be classified as young embedded sources. The remaining source, Haro 6-5B, is a disk source, having already dispersed its envelope.
On Optimum Methods in Quickest Detection Problems

In this paper optimum methods are developed for observing a process (1), in which the moment when a “disorder” $\theta$ appears is not known. The basic quantity characterizing the quality of this observation method is the mean time delay ${\boldsymbol \tau}$ for detection of a disorder.After making assumption (4) it is shown that for a given false alarm probability $\omega$ or for a given ${\bf N}$ — mathematical expectation of false alarm numbers occurring up to the moment the disorder appears — the observation method minimizing ${\boldsymbol \tau } = {\boldsymbol \tau } (\omega)$ or ${\boldsymbol \tau} = {\boldsymbol \tau} ({\boldsymbol N})$ is based on an observation of a posteriors probability (23). In § 3 a case is considered, wherein, the disorder appears on the background of steadystate conditions arising when the disorder is absent. A method is found for minimizing ${\boldsymbol \tau} = {\boldsymbol \tau} ({\bf T})$ for a set ${\bf T}$ — mathematical expectation of the time between two false alarms.
On the possible formation of Alfvén wings at Mercury during encounters with coronal mass ejections

The solar wind conditions near Mercury's perihelion, especially during Interplanetary Coronal Mass Ejection (ICME) events, will often be characterized by very low Alfvén Mach number (≤3). We suggest that the low Mach numbers and large north‐south magnetic fields during ICMEs will lead to the formation of “Alfvén wings” that will affect the configuration of the Hermean magnetosphere. It is shown that an electrical conductance threshold of about 5 S, comparable to the Alfvén conductance in the solar wind, is required for generation of Alfvén wings at Mercury. Assuming crustal conductances above this value it is demonstrated that currents in the Alfvén wings and closing across the planetary surface will produce significant perturbations (≥10 nT) of the magnetospheric magnetic field.
High-accuracy measurement of the 87Rb ground-state hyperfine splitting in an atomic fountain

We describe the operation of a laser-cooled rubidium 87Rb frequency standard. We present a new measurement of the 87Rb hyperfine frequency with a 1.3 × 10−14 relative accuracy, by comparison with a Cs fountain primary standard. The measured 87Rb ground-state hyperfine splitting is ν87 = 6 834 682 610.90429(9) Hz. This value differs from previously published values (see Essen L., Hope E. G. and Sutcliffe D., Nature 189 1961 298; Penselin S., Moran T., Cohen W. and Wscinkler G., Phys. Rev. 127 1962 524; Arditi M. and Cerez P. IEEE Trans. Instrum. Meas. IM-21 1972 391) by about 2 − 3 Hz and is 104 times more accurate. Because of the low collisional shift in 87Rb, future improvements may lead to a stability of 1 × 10−14τ−1/2 and a relative accuracy in the 10−17 range.
Loss of Water on the Young Venus: The Effect of a Strong Primitive Solar Wind☆

Abstract An enhanced primitive solar wind, such as may have prevailed during the first few 100 million years of the solar system history, is shown to have had the potential to stimulate strong thermal atmospheric escape from the young Venus. Due to heating by solar wind bombardment of an extended dense planetary corona, typically 10 times more extensive than the solid planet, an escape flux of pure atomic hydrogen as large as 3 × 1014cm−2sec−1is found to be possible, provided the solar wind was ≈103–104more intense than now. Even if escape was diffusion-limited, an enhanced primitive solar UV flux (a factor of ≈5 above present level), absorbed by ≈0.3 mbar of thermospheric water vapor, was able to supply the flow at the required rate. For these high escape rates, oxygen was massively dragged off along with hydrogen, and water molecules could be lost at a rate of ≈6 × 1013molecules cm−2sec−1. Because, at this rate, a terrestrial-type ocean was completely lost in ≈10 million years, short compared to typical accretion and outgassing times, water was lost “as soon” as it was outgassed. This mechanism could explain the present lack of oxygen in the Venus atmosphere. Because it is expected to affect all sunlike stars in the early phase of planet formation, abiotic oxygen atmospheres could be rare in the universe.
Weak Ferromagnetism in β-NaFeO2

The high temperature modification of sodium ferrite, β-NaFeO 2 , has weak ferromagnetism, whose Curie temperature is about 450°C. The magnetic property resembles that of LaFeO 3 . The origin of weak ferromagnetism of β-NaFeO 2 can be attributed to the presence of the Dzyalo-shinsky type interaction in this compound.
Scattering of light in a strongly magnetized plasma

The Thomson cross section in a strongly magnetized electron plasma is reexamined with a view to extending previous results of Canuto, Lodenquai, and Ruderman beyond the cold-plasma limit. To this end a formal relation is established between the differential photon cross section and the polarization currents induced in the medium by the incident photon. In the cold-plasma limit our formal approach leads to a substantially simplified differential cross section allowing an intuitive understanding of the scattering mechanism and the resulting anisotropy. For the integrated partial and total (summed over final polarizations) cross sections we recover previous results. The structure of this theory at and near the cyclotron resonance is examined including the necessary dissipative and broadening mechanisms. Extensions beyond the cold-plasma limit are discussed for the application to the problem of the accreting x-ray pulsars. Under conditions typical of the accretion column of some x-ray pulsars it is expected that the birefringent properties of the vacuum may significantly alter both the photon cross sections and the polarization properties of the radiation.
The early ultraviolet spectral evolution of Nova Cygni 1992

We report on the high resolution ultraviolet line profile evolution of Nova Cygni 1992 using the International Ultraviolet Explorer (IUE) satellite and the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). Our observations cover the period from discovery in 1992 February through 1993 April. The initial expansion velocity, derived from P Cyg profiles on Mg II and other resonance lines, was about 4500 km/s. All resonance transitions displayed P Cyg profiles around the time of UV maximum. We first discuss the spectral development as the initially optically thick atomic absorption curtain became optically thin. We then present the interpretation of the nebular spectral stage. The high resolution line profiles show that the shell rapidly developed nearly symmetric knots, or filaments, of emission. The optically thin transitions show an emission weighted expansion velocity of about 1800 km/s, consistent with the velocity inferred from the radio and infrared data. The emission lines display a symmetric set of filaments that appeared as soon as the line profiles became optically thin. The GHRS observations demonstrate that the filaments were located in the inner, slower moving parts of the ejecta. These probably record an initial low wave number instability imposed on the ejecta at the time of outburst. We suggest that the likely cause is a Rayleigh-Taylor instability. The emission at later stages is dominated by the filaments and, since this phenomenon is seen in virtually all novae, nebular line formation codes will have to account for the density inhomgeneities in order to adequately determine abundances for nove ejecta.
Internal Categories and Groupoids in Congruence Modular Varieties

Abstract It is well known that there exist several simple descriptions of the internal categories and groupoids in various classical algebraic categories such as groups, rings, Lie algebras, etc. One of those descriptions is extended to arbitrary congruence modular varieties: we describe all internal categories satisfying a certain commutator condition which always holds for internal groupoids, and for all internal categories in Mal'tsev (= congruence permutable) varieties. The results of this paper show a deep connection between internal category theory and commutator theory in universal algebra; the so-called Kiss difference operation also plays a central role.
Robust inference for variance components models for single trees of cell lineage data

Previously, Huggins and Staudte examined robust estimators for a variance components formulation of the bifurcating autoregressive model for cell lineage data. They gave asymptotic properties of the estimators if a large number of trees were observed. However, for single trees the derivation of these asymptotic properties is more complex. Here the asymptotic distributions of robust estimators of parameters associated with the stationary bifurcating autoregressive process as a single tree becomes large are obtained. These results follow from the formulation of the estimating functions as the product of a nonrandom matrix and the sum of vectors of functions of an infinite sequence of exchangeable random variables.
Initial trajectory model for a multi-maneuver moon to Earth abort sequence

To support the mission design and trajectory design problems associated with the moon-to-Earth trajectories for the crew exploration vehicle, a starting trajectory model that serves as the first iterate for a complete targeting and optimization procedure that takes a spacecraft from any closed lunar parking orbit to the Earth entry interface state for any date is developed. The motivation for this work is to examine the any-time abort capability required for human moon missions. The results presented here are limited to impulsive maneuvers. An analytical procedure is developed that constructs a multi-impulse escape trajectory from the moon propagated forward in time and a backward propagated trajectory from the Earth with a mismatch in position and velocity near the sphere of influence of the moon. The position and velocity discontinuities at the mismatch point are small enough to lie within the convergence envelope of a simple gradient based differential correction procedure that can, at a minimum, generate a feasible solution. This solution can then be analyzed further and serve as an initial estimate for an optimization procedure. The efficiency of the method is illustrated by solving any-time abort transfer problems typical for a human mission.
LensClean : an algorithm for inverting extended, gravitationally lensed images with application to the radio ring lens PKS 1830-211

We develop a new algorithm, LensClean, based on the Clean algorithm of radio astronomy, for consistently inverting partially or poorly resolved gravitational lens systems. The method is superior to previous algorithms, particularly when there is inadequate resolution in the observed image, and is significantly more effective at discriminating between good and bad lens models. We have applied LensClean to the 1.7 MHz Merlin and 8 MHz VLA maps of the radio ring lens PKS 1830-211. The quality of the inversions is largely limited by systematic errors in the radio maps, primarily the varying flux ratio of the two compact components
A self-matched wide scanning U-stub microstrip periodic leaky-wave antenna

A new type of printed periodic leaky-wave antenna is proposed, which is able to continuously scan a beam from backward to forward endfire. The unit cell consists of a microstrip line loaded with long lengths of transmission line folded as a U-stub and an interdigital capacitor. This U-stub geometry, which is characterized by a compact longitudinal size, permits operation at frequencies lower than other conventional periodic leaky-wave antennas. At the same time, the presence of the interdigital capacitor makes the radiating U-stub discontinuity self-matching, thus allowing for an elimination of open-stopband effects and for an achievement of an almost constant gain while the beam is scanned through broadside. A noteworthy aspect of the present design is that it represents the first periodic leaky-wave antenna that scans through broadside by radiating from the fundamental harmonic, without being a quasi-homogeneous metamaterial structure.
Continuous accumulation games on discrete locations

In an accumulation game, a HIDER attempts to accumulate a certain number of objects or a certain quantity of material before a certain time, and a SEEKER attempts to prevent this. In a continuous accumulation game the HIDER can pile material either at locations $1, 2, …, n, or over a region in space. The HIDER will win (payoff 1) it if accumulates N units of material before a given time, and the goal of the SEEKER will win (payoff 0) otherwise. We assume the HIDER can place continuous material such as fuel at discrete locations i = 1, 2, …, n, and the game is played in discrete time. At each time k > 0 the HIDER acquires h units of material and can distribute it among all of the locations. At the same time, k, the SEEKER can search a certain number s < n of the locations, and will confiscate (or destroy) all material found. After explicitly describing what we mean by a continuous accumulation game on discrete locations, we prove a theorem that gives a condition under which the HIDER can always win by using a uniform distribution at each stage of the game. When this condition does not hold, special cases and examples show that the resulting game becomes complicated even when played only for a single stage. We reduce the single stage game to an optimization problem, and also obtain some partial results on its solution. We also consider accumulation games where the locations are arranged in either a circle or in a line segment and the SEEKER must search a series of adjacent locations. © 2002 John Wiley & Sons, Inc. Naval Research Logistics, 49: 60–77, 2002; DOI 10.1002/nav.1048
Computation of Nielsen numbers for maps of closed surfaces

Let X be a closed surface, and let f : X ! X be a map. We would like to determine Min( f ) := min fj Fix g j : g ’ f g : Nielsen (cid:12)xed point theory provides a lower bound N ( f ) for Min( f ), called the Nielsen number, which is easy to de(cid:12)ne geometrically and is di(cid:14)cult to compute. We improve upon an algebraic method of calculating N ( f ) developed by Fadell and Husseini, so that the method becomes algorithmic for orientable closed surfaces up to the distinguishing of Reidemeister orbits. Our improve- ment makes tractable calculations of Nielsen numbers for many maps on surfaces of negative Euler characteristic. We apply the improved method to self- maps on the connected sum of two tori including classes of examples for which no other method is known. We also include the application of this algebraic method to maps on the Klein bottle K . Nielsen numbers for maps on K were (cid:12)rst calculated (geometrically) by Halpern. We include a sketch of Halpern’s never published proof that N ( f ) = Min( f ) for all maps f on K .