Miracle-dz/UniFAR-FTUs huggingface dataset:
Particle behavior in the turbulent boundary layer. I. Motion, deposition, and entrainment

The motion of solid particles near the wall in a turbulent boundary layer was investigated experimentally in a water flume by flow visualization techniques and by LDA. The particles were of polystyrene (specific density ∼1.05) with diameters ranging from 100 to 900 μm. Results show that particle motion, as well as entrainment and deposition processes, are controlled by the action of coherent wall structures, which appear to be funnel vortices. The behavior of the particles is consistent with the motion and effects of such vortices. The vortices appear to cause the formation of particle streaks near the wall, to create suitable conditions for particle entrainment, and to assist in particle deposition by conveying them from the outer flow to the wall region.
Direct methods for computing discrete sinusoidal transforms

According to Wang, there are four different types of DCT (discrete cosine transform) and DST (discrete sine transform) and the computation of these sinusoidal transforms can be reduced to the computation of the type-IV DCT. As the algorithms involve different sizes of transforms at different stages they are not so regular in structure. Lee has developed a fast cosine transform (FCT) algorithm for DCT-III similar to the decimation-in-time (DIT) Cooley–Tukey fast Fourier transform (FFT) with a regular structure. A disadvantage of this algorithm is that it involves the division of the trigonometric coefficients and may be numerically unstable. Recently, Hou has developed an algorithm for DCT-II which is similar to a decimation-in-frequency (DIF) algorithm and is numerically stable. However, an index mapping is needed to transform the DCT to a phase-modulated discrete Fourier transform (DFT), which may not be performed in-place. In the paper, a variant of Hou's algorithm is presented which is both in-place and numerically stable. The method is then generalised to compute the entire class of discrete sinusoidal transforms. By making use of the DIT and DIF concepts and the orthogonal properties of the DCTs, it is shown that simple algebraic formulations of these algorithms can readily be obtained. The resulting algorithms are regular in structure and are more stable than and have fewer arithmetic operations than similar algorithms proposed by Yip and Rao. By means of the Kronecker matrix product representation, the 1-D algorithms introduced in the paper can readily be generalised to compute transforms of higher dimensions. These algorithms, which can be viewed as the vector-radix generalisation of the present algorithms, share the in-place and regular structure of their 1-D counterparts.
The magnetic field of the helium-strong stars

We have conducted a search for magnetic fields in eight helium-strong stars, discovering strong magnetic fields in HD 37017, HD 37776, HD 58260, HD 64740, and HD 96446. With the previous discovery of a magnetic field in sigma Ori E this brings to six (out of nine observed ) the number of magnetic helium-strong stars. This result confirms the hypothesis that the helium-strong stars are a hot extension of the Ap phenomenon. We consider the possibility that mass loss on the main sequence is responsible for the apparent division among the helium stars into rapid and slow rotators, but conclude that such mass loss is probably incapable of significantly slowing down a rapidly rotating helium-strong star.
A study of circumstellar envelopes around bright carbon stars. I: Structure, kinematics, and mass-loss rate

We have performed a survey of circumstellar CO emission on a sample of bright carbon stars, which is relatively complete out to about 900 pc from the Sun. In total, 68 detections were made. All objects within 600 pc of the Sun were detected. The result suggests that the large majority of all carbon stars have circumstellar envelopes. The CO-emitting parts of these envelopes appear to have angular sizes less than about 15″. The median gas expansion velocity is 12.5 km s −1 , and the expansion velocities for the majority of the objects fall in the range 9-15 km s −1 . We find no significant differences between the expansion velocities estimated from the CO (1-0) and CO (2-1) lines. The expansion velocities show a tendency to be higher for stars that lie close to the Galactic plane
Diffusive Transport by Breaking Waves

Abstract A simple conceptual model of the relationship between advective transport by breaking waves and diffusive transport is derived. line model postulates that the displacement of fluid parcels by a breaking wave is analogous to molecular diffusion (in a manner similar to conventional mixing length theory). Unlike molecular diffusion, in which the fluctuations of nearby particles are independent, in fluid flow the motion of nearby parcels can be coherent. The effectively random phase of wavebreaking events with respect to an individual particle, however, results in a macroscopic “random walk” of the parcel with a step size related to the width of the breaking wave and a timescale related to the frequency of wave breaking events. As in the case of molecular diffusion, the motion of individual molecules or fluid parcels is unpredictable (chaotic, in fact), but averaging over a large ensemble of parcels results in an ensemble variance that increases linearly with time, formally equivalent to molecular di.
Image Formation for Coherent Diffuse Objects: Statistical Properties

The properties of the amplitude and illuminance of the images of coherently illuminated diffuse objects are studied. Uniform and nonuniform objects are considered. The image illuminance is considered to result from a linear transformation of a nonstationary gaussian stochastic process followed by a square-law detection. Expressions are obtained for the mean, autocorrelation, variance, and spatial power spectral density of the amplitude and of the illuminance. Interpretation of the results led to conclusions concerning the speckle size, the noise power in the image, and the transfer function of an optical system when the object diffuses coherent light. When the autocorrelation width of the random fluctuations of the object amplitude is small compared to the impulse response of the system, the mean illuminance in the image plane is that which would be given by an incoherent object having the same luminance as the object considered; the average speckle size is equal to that of the impulse response of the system; the average transfer function of the system is the incoherent transfer function; and the distribution of the noise spatial frequencies does not depend upon the form of the signal, but only upon its total energy. Other results concerning the image statistics have also been obtained.
Stability analysis of the quasideffusion and second moment methods for iteratively solving discrete-ordinates problems

Abstract We consider two previously-published methods for obtaining iterative solutions of discrete-ordinates problems, the nonlinear “quasidiffusion” method developed by Gol'din1, and the “second moment” method proposed by Lewis and Miller2. We describe these methods, show that they reduce to almost the same (linear) method for a special class of problems, and perform a Fourier stability analysis of the two methods for these special problems. This analysis shows that the two methods are stable and rapidly converging for all mesh sizes. We confirm these theoretical predictions by presenting results from direct numerical calculations involving the methods.
Antiferro‐ferromagnetic transition and microstructural properties in a sputter deposited FeRh thin film system

Magnetic and microstructural properties are studied in sputter deposited Fe100−xRhx alloy (28.0<x<57.0) thin films. As‐deposited films show a preferred (111) oriented fcc phase at x≳35.0. Annealing at 600 °C results in the CsCl type structure which exhibits a preferred (110) orientation with the same lattice constant as that of bulk. However, an incomplete antiferro‐ferromagnetic transition with large thermal hysteresis is observed in a wider composition range (x≳45.4) than bulk. Furthermore, magnetization at room temperature decreases continuously from x=35.0 to x=57.0 in contrast to the sharp drop at x=50 in bulk. By using scanning and transmission electron microscopy and Mossbauer spectroscopy, it is found that the retained fcc phase and compositional fluctuation strongly affect the magnetic transition. The retained fcc phase surprisingly reduces the grain growth of the CsCl type ordered phase from 4000 to 300 A as the Rh content increases from 45.4% to 54.0%.
An efficient frame selection approach to variable frame rate analysis for noise robust speech recognition

This paper presents a low‐complexity, effective variable frame rate (VFR) analysis method that conducts frame selection on the basis of a posteriori signal‐to‐noise ratio (SNR) weighted energy distance. It has two characteristics. First, energy distance (instead of cepstral distance) is used to make it computationally efficient and thus enable a finer granularity in search as compared with cepstral distance criterion. Secondly, SNR weighting is used to emphasize the reliable regions in noisy speech signals. In terms of frame selection, it is experimentally found that the method is able to assign a higher frame rate to fast changing events such as consonants, a lower frame rate to steady regions like vowels and no frames to silence, even for very low SNR signals. The VFR method is applied to speech recognition in noisy environments to improve noise robustness. Being a method that takes effect in the time‐domain, it is moreover combined with spectral‐ and cepstral‐domain techniques to gain further improvement. Experiments are conducted on the Aurora 2 database, which is the TI digits database artificially distorted by adding different noises, and very encouraging results are obtained.
How to Lie with Statistics

Darrell Huff runs the gamut of every popularly used type of statistic, probes such things as the sample study, the tabulation method, the interview technique, or the way the results are derived from the figures, and points up the countless number of dodges which are used to full rather than to inform.
Correlations between UBV colors and fine structure in E and S0 galaxies: A First attempt at dating ancient merger events

A study of 69 E and S0 galaxies located mostly in the field and in groups reveals that the UBV colors become systematically bluer at any given luminosity as the amount of merger-induced fine structure increases. To quantify such fine structure, we define an index Σ that measures ripples, jets of luminous matter, X structures, and boxy isophotes; it ranges between 0 and 7.6 for the above galaxies. The correlations between UBV colors and this index Σ closely resemble the correlations found earlier between CN, Mg 2 , and Hβ line strengths and the same Σ in 36 ellipticals [Schweizer et al. ApJ, 364, L33 (1990)]
The effect of various source signal properties on measurements of the interaural crosscorrelation coefficient

Measurements that attempt to predict the perceived spatial impression of musical signals in concert halls typically are conducted by calculating the interaural cross-correlation coefficient (IACC) of an impulse response. The causes of interaural decorrelation are investigated and it is found that this is affected by frequency dependent interaural time and level differences and variations in these over time. It is found that the IACC of impulsive and of narrowband tonal signals can be very different from each other in a wide range of acoustical environments, due to the differences in the spectral content and the duration of the signals. From this, it is concluded that measurements made of impulsive signals are unsuitable for attempting to predict the perceived spatial impression of musical signals. It is suggested that further work is required to develop a set of test signals that is representative of a wide range of musical stimuli.
A theory of second occurrence focus

This paper proposes to analyse second occurrence foci as foci whose domain is properly contained in the background of another focus domain, and linearly follows the last focus of that domain. It is shown that general assumptions about the representation and prosodic realisation of focus predict that foci with these properties will be realised by stress, but not pitch accent, i.e. as second occurrence foci. Furthermore, whether a focus domain is subordinated in this sense follows from general principles of focus assignment and interpretation. No assumptions specific to second occurrence foci are required to explain the phenomenon. The analysis relies on, and thus indirectly supports, the assumptions that focus/background, rather than new/given are the relevant concepts in stress and accent assignment, and that focus realisation is mediated by prosodic, particularly metrical, structure.
ON THE LOW-LEVEL WIND STRUCTURE OF TROPICAL STORMS

Abstract Data from a number of reconnaissance flights into large Pacific tropical cyclones are combined to obtain a generalized pattern of winds at low level (about 1000 feet) under both stationary and non-stationary conditions. With these winds, a number of dependent computations are made including relative trajectories, divergence, vertical motion, rainfall, energy, and relative vorticity.
Analytic solution of liquid-drop impact problems

The pressure in an impacting liquid drop against both a rigid and an elastic target is calculated for the period when the contact region is expanding faster than the wave speed in the liquid. For very low speed impact a geometrical-acoustics model is shown to give a good representation of the solution, until the edge speed approaches the wave speed. A self-similar solution, that takes account of nonlinear effects, is used in the neighbourhood of the contact edge. Comparisons are made with linear theory and numerical calculations. It is shown that linear theory is totally inadequate in predicting the escape of the shock system from the contact edge and that numerical calculations have used too large a time step to calculate the time of escape correctly. The delay in escape time from the previous theoretical predictions of Heymann (1969) is attributed to the elasticity of the target, an effect that is taken into account in the present work.
Optical response of a single noble metal nanoparticle

The characterization of a single metal nanoobject by comparing its theoretical and experimental far-field spectra measured by a spatial modulation spectroscopy (SMS) technique is discussed in the case of gold and silver nanoparticles. Quantitative determination of the polarization dependent absorption cross-section spectrum of a single nanoparticle is shown to permit its optical identification, i.e., determination of its shape, size and orientation on a surface.
Some Relationships between the Binomial Error Model and Classical Test Theory

Straightforward application of the binomial error model defines parallel forms as random samples of items from a large pool of items. Such a model includes form-to-form differences in difficulty as a component of error variance and leads to Kuder-Richardson formula 21 as an estimate of reliability. Such a component is inappropriate if all examinees take the same form of the test. It is demonstrated here that if the form-to-form component is removed from the estimate of average error variance, the binomial model leads to KR 20 as the estimate of reliability. Empirical data are cited which support deductions from the compound binomial error model regarding the trend in the standard error of measurement over the observed score range. A computational formula derived from this model is recommended for two practical purposes: to estimate the standard error for individual examinees or to implement the recommendation in the APA/AERA/NCME Standards (1974) that the standard error of measurement be reported for several score levels.
A Discussion of Population Invariance of Equating

This article discusses the five studies included in this issue. Each article addressed the same topic, population invariance of equating. They all used data from major standardized testing programs, and they all used essentially the same statistics to evaluate their results, namely, the root mean square difference and root expected mean square difference (Dorans & Holland, 2000). The major premises underlying all of these articles are that population invariance is a prerequisite for equating, and lack of population invariance can be taken as evidence that a linking is not an equating.
Adaptive grazing incidence optics for the next generation of x-ray observatories

Advances in X-ray astronomy require high spatial resolution and large collecting area. Unfortunately, X-ray telescopes with grazing incidence mirrors require hundreds of concentric mirror pairs to obtain the necessary collecting area, and these mirrors must be thin shells packed tightly together. They must also be light enough to be placed in orbit with existing launch vehicles, and able to be fabricated by the thousands for an affordable cost. The current state of the art in X-ray observatories is represented by NASA's Chandra X-ray observatory with 0.5 arc-second resolution, but only 400 cm2 of collecting area, and by ESA's XMM-Newton observatory with 4,300 cm2 of collecting area but only 15 arc-second resolution. The joint NASA/ESA/JAXA International X-ray Observatory (IXO), with ~15,000 cm2 of collecting area and 5 arc-second resolution which is currently in the early study phase, is pushing the limits of passive mirror technology. The Generation-X mission is one of the Advanced Strategic Mission Concepts that NASA is considering for development in the post-2020 period. As currently conceived, Gen-X would be a follow-on to IXO with a collecting area ≥ 50 m2, a 60-m focal length and 0.1 arc-second spatial resolution. Gen-X would be launched in ~2030 with a heavy lift Launch Vehicle to an L2 orbit. Active figure control will be necessary to meet the challenging requirements of the Gen-X optics. In this paper we present our adaptive grazing incidence mirror design and the results from laboratory tests of a prototype mirror.
The Seesaw in Winter Temperatures between Greenland and Northern Europe. Part I: General Description

Abstract We have investigated the well-known tendency for winter temperatures to be low over northern Europe when they are high over Greenland and the Canadian Arctic, and conversely. Well-defined pressure anomalies over most of the Northern Hemisphere are associated with this regional seesaw in temperature, and these pressure anomalies are so distributed that the pressure in the region of the Icelandic low is negatively correlated with the pressure over the North Pacific Ocean and over the area south of 50°N in the North Atlantic Ocean, Mediterranean and Middle East, but positively correlated with the pressure over the Rocky Mountains. The composite patterns of pressure anomalies in the seesaw are almost identical to the fist eigenvector in the monthly mean pressure, but the standard deviations of pressure anomalies in seesaw mouths are as large as the standard deviations of monthly means in general. Since 1840 the seesaw, as defined by temperatures in Scandinavia and Greenland, occurred in more than 40%.
EVALUATION OF POTENTIAL-VORTICITY CHANGES NEAR THE TROPOPAUSE AND THE RELATED VERTITCAL MOTIONS, VERTICAL ADVECTION OF VORTPCITY, AND TRANSFER OF RADIOACTIVE DEBRIS FROM STRATOSPHERE TO TROPOSPHERE

Abstract Individual potential-vorticity change, vertical motion, vertical advection of vorticity and flow from stratosphere to troposphere are evaluated at different levels and for different times in an extratropical disturbance. Vertical motions are obtained from trajectories on three isentropic surfaces for two different times. The isentropes pass through or near a front in the upper troposphere, the lower stratosphere, and the high troposphere on the cold side of the front. Vertical motion is also evaluated at 500 mb from an adiabatic method designed to give instantaneous values to the extent that the system moves without change of shape. Negative extremes of 8 to 10 cm sec−1 occur in the upper-air front, with positive extremes of the same magnitude a short distance to the northeast, coinciding with the eastern exit of the frontal zone. From theory, it is shown that potential vorticity is not conserved if there is either a gradient of diabatic heating or a component of curl, normal to the isentropic su.
SPECTROSCOPY OF CARBON STARS IN THE DRACO AND URSA MINOR DWARF SPHEROIDAL GALAXIES

With the ISIS spectrograph on the William Herschel Telescope, we obtained intermediate-resolution optical spectra in three and five carbon stars belonging to the dwarf spheroidal (dSph) galaxies Draco and Ursa Minor, respectively. The metallicity, carbon isotopic ratios, and high-mass s-element abundances were determined by spectral synthesis in LTE using appropriate spherically symmetric, carbon-rich atmosphere models. The infrared colors and derived luminosities suggest that these stars are equivalent to the classical CH-type stars found in the halo of the Milky Way, although the evidence of luminosity variations in the stars Draco 461 and Draco 20733 may be compatible with these being carbon-rich low-mass asymptotic giant branch stars. The derived overall metallicity in the stellar sample ([M/H] ∼−2.0) agrees with the average metallicity of the main stellar component in these dSphs obtained by previous studies. The C/O and 12C/13C ratios, and the average large heavy-element (Ba, La, Nd, Sm) enhancements derived ([hs/M] ⩾1) are also similar to the values found in galactic CH-type stars at the same stellar metallicity. Although this average excess in heavy elements can be explained by standard s-process nucleosynthesis models, in two stars of Ursa Minor there is a suggestion that their heavy-element abundance pattern bears a closer resemblance to the scaled solar system r-process than the s-process abundance curve. If this is confirmed, these stars would represent an extragalactic example of the s + r carbon-rich (binary) stars found in the galactic halo. This r-process like abundance pattern has been found previously in other red giant stars belonging to Ursa Minor, suggesting a peculiar chemical evolution history in this dSph galaxy.
Optimization‐based material parameter identification in indentation testing for finite strain elasto‐plasticity

The calculation of the derivatives of the state variables with respect to material parameters using the direct differentiation method is developed for the case of a finite strain finite element analysis in corotational formulation for material behaviour including hypo‐elasticity and non‐linear isotropic and kinematic hardening plasticity. The sensitivity analysis for the case of flexible‐to‐flexible contact, required in indentation testing, has been included. The derivatives obtained in a rotating‐stretching bar problem are compared to results obtained by the finite difference method in order to verify the suitability of the corotational formulation in sensitivity analysis for dealing with rigid body rotations. Material parameter identification using a gradient‐based numerical optimization procedure is assessed with respect to stability by using pseudo‐experimental indentation curves, obtained from modelling with known material parameters, and superposed with artificial noise. The effect of the load history on parameter identification is investigated.