Miracle-dz/UniFAR-FTUs huggingface dataset:
Controlling Type I Error Rates in Assessing DIF for Logistic Regression Method Combined With SIBTEST Regression Correction Procedure and DIF-Free-Then-DIF Strategy

The simultaneous item bias test (SIBTEST) method regression procedure and the differential item functioning (DIF)-free-then-DIF strategy are applied to the logistic regression (LR) method simultaneously in this study. These procedures are used to adjust the effects of matching true score on observed score and to better control the Type I error rates of the LR method in assessing DIF, respectively. The performance and the detailed procedure, including anchor length, of the newly proposed method are investigated through a series of simulation studies. The results show that the standard LR method yielded inflated Type I error rates as the percentage of DIF items or group ability differences increased, whereas the newly proposed method produced less inflated results. It controlled Type I error rates well in these conditions as the length of anchor increased. However, the usually suggested one-anchor or four-anchor rule of the DIF-free-then-DIF strategy is not long enough for methods that use the raw score as the matching variable. In general, the newly proposed method with eight anchor items yielded well-controlled Type I error rates under all study conditions, even with 40% DIF items in the test and a group ability difference equal to one standard deviation. It is recommended that both the SIBTEST correction procedure and the DIF-free-then-DIF strategy be applied to the LR method when assessing DIF.
Piezoelectricity in uniaxially stretched poly(vinylidene fluoride)

Hysteresis characteristics, which are similar to those observed in ferroelectric crystals, are found in uniaxially stretched poly(vinylidene fluoride) under a high electric field above 300 kV/cm at room temperature. The electrostrictive constant q13 in poly(vinylidene fluoride) is determined for polarization below about 0.5 μC/cm2 at room temperature to be 0.9 cgs esu. The remanent polarization after the poling process can be easily eliminated with a sufficiently high sinusoidal electric field. This effect is confirmed by thermally stimulated currents before and after the depolarization process.
Structural phase transformation through defect cluster growth in Gd-doped ceria

Defect clusters with ordered structures in Gd-doped ceria have been veriﬁed by transmission electron microscopy. Atomistic simulation validates further the ordered structures and related pathway for cluster growth. A unique dumbbell structure formed with six oxygen vacancies in a ceria matrix has been identiﬁed as the building block for defect cluster growth and sequentially for the evolution from a F- to C-type lattice. As such, the phase transformation as established on the atomic scale occurs through this defect cluster growth.
The formation of protostellar disks. 2: Disks around intermediate-mass stars

Hydrodynamical calculations of the evolution of a collapsing, rotating axisymmetric 10 solar masses molecular clump, including the effects of radiative acceleration but without magnetic fields, are represented. The initial cloud is assumed to be uniformly rotating, centrally condensed sphere with rho is proportional to r(exp -2). Several cases are considered, in which both the overall clump size and the total amount of angular momentum are varied. The calculations show how a warm, quasi-hydrostatic disk surrounding a central unresolved core of only a few solar masses forms and grows in size and mass. The disk is encased in two distinct accretion shock fronts, both of which are several scale heights above the equatorial plane. At the end of the calculation of our standard case, the central unresolved region is found to have a mass of 2.7 solar masses and a ratio of rotational to gravitational energy of approximately 0.45, sufficiently large to be unstable to nonaxisymmetric perturbations. In addition, the inner portions of the disk containing most of the mass are unstable according to the local Toomre criterion, implying that also in this region nonaxisymmetric perturbations will lead to rapid evolution. Under the assumption that gravitational torques would transport angular momentum out of this region, a central core of less than or approximately 8 solar masses with a stable disk of greater than or approximately = 2 solar masses should result. Frequency-dependent radiative transfer calculations of the standard case at selected ages show how the continuum spectrum of the structure depends on the disk's orientation and age and how the observed isophotal contours vary with wavelength. Because of the strong dependence on viewing angle, continuum spectra alone should not be used to estimate the evolutionary stage of development of these objects. Comparable results were obtained for the other cases considered.
Possible half-metallic ferromagnetism in zinc blende CrSb and CrAs (invited)

Theoretical study based on a first-principles band structure calculation is carried out for new room-temperature ferromagnets, zinc blende CrSb and CrAs. It is found from the total-energy calculation that the ferromagnetic state is energetically favorable for both materials. By using the value of the difference in total energy between ferromagnetic and the antiferromagnetic states, the Curie temperatures of these ferromagnets are estimated as 1600–1800 K within mean-field approximation of the Heisenberg model. The magnetic moment is evaluated to be 3 Bohr magnetons per formula unit for both materials, which agrees well with the saturation moments estimated experimentally. Furthermore, these ferromagnets are half metallic, and the spin polarization at the Fermi level is almost unaffected even if spin–orbit interaction is taken into account.
A formulation of a wave‐activity flux for stationary Rossby waves on a zonally varying basic flow

A new formulation of an approximate conservation relation is proposed for stationary Rossby waves on a zonally varying basic flow, utilizing that A (proportional to wave enstrophy) and ε (proportional to wave energy) are both related to the wave activity pseudomomentum. For stationary Rossby waves, it is shown in the limit of a small‐amplitude, plane wave on a slowly varying, unforced non‐zonal flow that a particular linear combination of A and ε, namely, M ≡ (A + ε)/2, is independent of the wave phase, even if unaveraged, and is conserved under steady, unforced and nondissipative conditions. It is also shown that the three‐dimensional flux of M is parallel to the local group velocity in the WKB limit. The flux could be a useful diagnostic tool, as shown in an example that presents a “snapshot” of the three‐dimensional propagation of a stationary Rossby wavetrain in the real atmosphere. Our conservation relation is a generalization of that for stationary Rossby waves on a zonally‐uniform basic flow derived by Plumb.
Propagation of waves along an impedance boundary

A theoretical analysis of the scalar wave field due to a point source above a plane impedance boundary is presented. A surface wave is found to be an essential component of the total wave field. It is shown that, as a result of ducting of energy by the surface wave, the amplitude of the total wave near the boundary can be greater than it would be if the boundary were perfectly reflecting. Asymptotic results, valid near the boundary, are obtained both for the case of finite impedance (the soft‐boundary case) and for the limiting case in which the impedance becomes infinite (the hard‐boundary case). In the latter, the wave amplitude in the farfield decreases essentially as r−1, where r is the horizontal propagation distance; whereas in the former (if the surface‐wave term is neglected) it decreases as r−2. The results obtained here are compared with results of experimental studies of sound propagation along boundaries, and it is suggested that some apparently anomalous experimental findings might be explain.
Characteristics of orifices for modeling nonlinear power take-off in wave-flume tests of oscillating water column devices

Oscillating water column (OWC) devices for wave power extraction are appealing, but are still in need of research. In this study, a series of wave-flume experiments was conducted to examine the hydrodynamic performance of a rectangular OWC device fixed in regular waves. Two types of orifices, slot orifices and circular orifices, were used to simulate the nonlinear power take-off (PTO) mechanism, and the effects of orifice geometry were examined. A two-point measurement method was proposed to reconstruct the instantaneous spatial profile of the water surface inside the OWC chamber for reducing bias in the measured wave power extraction efficiency. The flow characteristics of PTO were described by a quadratic loss coefficient, and our experimental results showed that the quadratic loss coefficient of the slot orifices varied with wave period and slot geometry. Empirical formulas were proposed for the quadratic loss coefficients of the two types of orifices. The ability to determine the quadratic loss coefficient of an orifice will allow us to design orifices for small-scale tests and calculate the power extraction using only pressure measurement. Our results also suggested that the pressure coefficient should be more reliable than the amplification coefficient as an indicator of the power extraction performance of an OWC device.
A semi-analytical method for the analysis of pile-supported embankments

In this paper, a semi-analytical method for the analysis of pile-supported embankments is proposed. The mathematic model describes the cooperative behavior of pile, pile cap, foundation soil, and embankment fills. Based on Terzaghi’s 1D consolidation theory of saturated soil, the consolidation of foundation soil is calculated. The embankments with two different types of piles: floating piles and end-bearing piles are investigated and discussed. The results of axial force and skin friction distributions along the pile and the settlements of pile-supported embankments are presented. It is found that it takes a longer time for soil consolidation in the embankment with floating piles, compared with the case using end-bearing piles. The differential settlement between the pile and surrounding soil at the pile top is larger for the embankment with end-bearing piles, compared with the case of floating piles.
First Detection of Submillimeter Polarization from T Tauri Stars

We report a first detection of polarization of the 850 μm continuum emission from two T Tauri stars (TTSs), GM Aur and DG Tau. These are both single and classical TTSs. The emission mostly comes from the compact (r < 100 AU) accretion disks. The polarization (at ~3% level at 3 σ) is interpreted in terms of thermal emission by magnetically aligned dust grains in the disk. Thus these submillimeter polarizations probe the magnetic field structure in the disk, while the previously reported millimeter/submillimeter polarizations of protostars and the transitional objects from the protostars to TTSs trace the magnetic fields in the larger envelope region. In both TTSs, the direction of the magnetic field inferred from our submillimeter polarizations is parallel to the plane of the compact dust disk measured by interferometric observations, suggesting the dominance of a toroidal magnetic field component in the disk. The magnetic evolution of the circumstellar environments is discussed, as well as the constraints on the MHD models of the jets and outflows from young stellar objects.
Numerical Study of Microscale Monopropellant Fuel Injection Using Two-Phase Slug Formation

Gas and liquid converging at a microchannel cross junction results in the formation of periodic, dispersed microslugs. This microslug-formation phenomenon has been proposed as the basis for a fuel-injection system in a novel, discrete monopropellant microthruster design for use in next-generation miniaturized satellites. Experimental work by McCabe et al. (“A Micro-Scale Monopropellant Fuel Injection Scheme Using Two-Phase Slug Formation,” Journal of Propulsion and Power, Vol. 27, No. 6, 2012, pp. 1295–1302) demonstrated the ability to generate fuel slugs with characteristics commensurate with the intended application. In this work, numerical modeling and simulation is used to further study this problem and identify the sensitivity of the slug characteristics to key material properties including surface tension, contact angle, and fuel viscosity. These concerns are of practical concern for this application due to the potential for thermal variations and/or fluid contamination during typical operation. For.
Infrared flux method and colour calibrations

The Infrared Flux Method (IRFM) is one of the most accurate techniques to derive fundamental stellar parameters – namely effective temperatures, bolometric luminosities and angular diameters – in an almost model independent way. We review the method and its application to late-type dwarfs, with particular emphasis on the dependence of the resulting effective temperatures on the adopted absolute calibration. We also compare our results with a large set of recent interferometric angular diameters in order to better constrain the temperature scale: despite the excellent agreement we find, uncertainties of order 100 K cannot yet be ruled out. We conclude that although such disturbing uncertainty still plagues the determination of accurate effective temperatures, the homogeneous and internally precise fundamental stellar parameters determined via IRFM permit the study of the fine structure of the lower main sequence in greater detail than ever before.
Characterization of the mean velocity of a circular jet in a bounded basin

A circular jet has broad and important applications in practical engineering. Most research in this area has focused on a free jet, a wall jet or a vertical jet in a bounded domain. In this study, the mean velocities of circular offset jets were studied for four jet exit Froude numbers (Fr), three offset heights (S) (S/d=1, 2, 3) and three submergence ratios (ht/S) (surface jet, mixed jet, and submerged jet) in a bounded basin. Based on the results, we propose a velocity decay formula for a circular jet. The lateral velocity spread was more consistent with Gaussian and Cauchy–Lorentz distributions than the vertical velocity. Moreover, Fr had little effect on the decay of the mean velocity for a circular jet when Re>1×104. The lateral and vertical spreads showed a quadratic relationship with the streamwise distance for different values of Fr at X/d<10. The positions of maximum mean velocity decay were independent of Fr and S/d when X/d<10. The spread rate was more uniform in the lateral direction than that in the vertical direction in a certain region for different S/d and ht/S. Therefore, the decay, spread, and maximum velocity position of the mean velocity for a circular offset jet can remain stable under different values of Fr, offset height, and submergence ratio.
Changing pupils' attitudes to careers in science

Factors that affect students' attitudes to school science and to careers in science are many and varied, depending on the individual student. This study analyses the attitudes of students from age 11 to 16 towards such careers and the effect of school science on those attitudes. It discusses the implications for teaching in the context of motivational factors, and highlights the need to allow students space to match their own motivational needs.
Residual misalignments of the Keck Telescope primary mirror segments: classification of modes and implications for adaptive optics

Because of limitations in the alignment process resulting from the telescope active control system and from atmospheric turbulence, the segments of the Keck Telescope primary mirror are never perfectly aligned. We describe a scheme for classifying these misalignments in terms of modes of the primary mirror. We describe these modes in terms of noise propagation, symmetry (specifically their resemblance to Zernike polynomials), and how discontinuous they are. Modal spectra of typical mirror misalignments are presented. The edge discontinuities which result from these misalignments are significantly smaller than what one would expect from random, uncorrelated tip/tilt errors of the same size, a fact which may have important implications for adaptive optics systems on segmented mirror telescopes.
Bearing capacity of thin-walled shallow foundations: an experimental and artificial intelligence-based study

Thin-walled spread foundations are used in coastal projects where the soil strength is relatively low. Developing a predictive model of bearing capacity for this kind of foundation is of interest due to the fact that the famous bearing capacity equations are proposed for conventional footings. Many studies underlined the applicability of artificial neural networks (ANNs) in predicting the bearing capacity of foundations. However, the majority of these models are built using conventional ANNs, which suffer from slow rate of learning as well as getting trapped in local minima. Moreover, they are mainly developed for conventional footings. The prime objective of this study is to propose an improved ANN-based predictive model of bearing capacity for thin-walled shallow foundations. In this regard, a relatively large dataset comprising 145 recorded cases of related footing load tests was compiled from the literature. The dataset includes bearing capacity (Qu), friction angle, unit weight of sand, footing width, and thin-wall length to footing width ratio (Lw/B). Apart from Qu, other parameters were set as model inputs. To enhance the diversity of the data, four more related laboratory footing load tests were conducted on the Johor Bahru sand, and results were added to the dataset. Experimental findings suggest an almost 0.5 times increase in the bearing capacity in loose and dense sands when Lw/B is increased from 0.5 to 1.12. Overall, findings show the feasibility of the ANN-based predictive model improved with particle swarm optimization (PSO). The correlation coefficient was 0.98 for testing data, suggesting that the model serves as a reliable tool in predicting the bearing capacity.
Minkowskian Solution of General Relativity with Cosmological Constant and the Accelerating Universe

A Minkowskian solution of the equation of General Relativity (as written by Einstein in 1915) is trivial because it simply means that both members of the equation are equal to zero. However, if alternatively, one considers the complete equation with a non-zero constant Λ (Einstein 1917), a Minkowskian solution is no longer trivial because it amounts to impose a constraint on the right hand side of the equation (i.e. a non-null stress-energy tensor). If furthermore one identifies (as usual) this tensor to the one of a perfect fluid, one finds that this fluid has a positive energy density and a negative pressure that depend on the three constants of the equation (i.e. gravitational constant G, cosmological constant Λ and velocity of light c). When doing that (§1), one has to consider the “Minkowskian Vacuum” as a physical object of GR (an enigmatic non-baryonic Minkowskian fluid). Can one build a model of this object on the basis of a dynamical equilibrium between the effective gravitational attraction due to the positive energy density versus the negative pressure repulsion? We propose to study such a model, where the (enigmatic) fluid is assumed to exist only in a limited sphere whose surface acts like a “test body” sensitive to the gravitational field created by the fluid. No static equilibrium exists, but a pseudoNewtonian “dynamical equilibrium” (§2) can be reached if the pseudoEuclidean fluid is in state of expansion. Up to there, we have simply constructed a model of an “abstract Universe” (i.e. the limited sphere: There is no fluid outside this sphere! ) that gives to a (purely mathematical) constant Λ a concrete physical meaning. We discover finally that our expanding fluid has not only dynamical (gravitational) properties (§3) but also optical properties that are connected with Doppler Redshift (§4). Remembering that recent observations in Cosmology indicate that the “real Universe” seems to be “Flat” and in “Accelerated Expansion”; remembering also (after all) that the archetypal Flat Universe is simply a Minkowskian Universe, we logically wonder if the unexpected Minkowskian global solution, could not be also a significant cosmological model (conclusion).
Proof-of-principle demonstration of Nb3Sn superconducting radiofrequency cavities for high Q0 applications

Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. This contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb3Sn. In this paper, we present results for single cell cavities coated with Nb3Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q0 out to medium fields was reproducible, resulting in an average quench field of 14 MV/m and an average 4.2 K Q0 at quench of 8 × 109. In each case, the peak surface magnetic field at quench was well above Hc1, showing that it is not a limiting field in these cavities. The coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that—taking i.
Creeping flow around a sphere in a shear flow close to a wall

The creeping flow around a sphere close to a wall is calculated by revisiting the bipolar coordinates solution technique. The coefficients in the expansions of the spherical harmonics are easily calculated from two recurrence relationships, following the idea of O'Neill and Bhatt. That is, there is no need to solve successively larger truncated linear systems to obtain the coefficients, as was done in earlier papers for a sphere translating along a wall by (O'Neill) or rotating by (Dean and O'Neill) and for a shear flow around a fixed sphere by (Tozeren and Skalak). Consequently, results can be obtained even for small gaps between the sphere and the wall without excessive computer resources. Thus, the present technique provides a reference to obtain all the friction coefficients and flow fields with excellent precision. Results for the friction coefficients are given with up to 17 significant digits for later reference