Miracle-dz/UniFAR-FTUs huggingface dataset:
The relation between velocity dispersion and temperature in clusters: Limiting the velocity bias

The observed galaxy velocity dispersion in clusters of galaxies is compared with the X-ray temperature of the intracluster gas for a large sample of clusters. A strong correlation is found between the observables which is best fitted by the relation σ=332±52(k T) 0.6±0.1 km s −1 ; here σ is the rms radial velocity dispersion in the cluster, and kT is the gas temperature in keV. The relation is consistent with that expected from an isothermal model where both the gas and the galaxies are in hydrostatic equilibrium with the binding cluster potential, i.e., σ∞T 0.5
A practical affine equivariant multivariate median

A robust affine equivariant estimator of location for multivariate data is proposed which becomes the univariate median for data of dimension one. The estimator is robust in the sense that it has a bounded influence function, a positive breakdown value and has high efficiency compared to the sample mean for heavy-tailed distributions. Perhaps its greatest strength is that, unlike other affine equivariant multivariate medians, it is easily computed for data in any practical dimension. Copyright Biometrika Trust 2002, Oxford University Press.
RADIATION CHEMISTRY OF HEAVY PARTICLE TRACKS. I. GENERAL CONSIDERATIONS

The radiation chemistry of heavy-particle tracks in dilute aqueous solution is considered in a unified manner. Emphasis is on the physical and chemical phenomena which are involved rather than on the construction of models to be used in actual calculations although the latter problem is discussed. A differential segment of a heavy-particle track is composed of two parts which we call core and penumbra; elementary considerations show that all properties of such a differential track can be uniquely specified in terms of a two-parameter system, and we choose energy per nucleon (E) and atomic numbers (Z) as independent parameters. The nature of heavy-particle-track processes varies with the magnitude of the energy deposit (LET), and we discuss three categories of track problems, for low-, intermediate-, and high-LET cases, respectively. Scavenger reactions normally terminate radical recombination in a track, and for heavy-particle tracks we find a criterion involving the scavenger concentration for a convenient separation of core and penumbra into essentially noninteracting parts which can be treated independently. Problems of the core expansion in the three regions are considered, and it is found that a versatile model can be constructed on concepts previously introduced by Ganguly and Magee. A model for themore » penumbra, based on the authors' electron-track theory, is presented and discussed. « less
Assessing-To-Learn: Formative Assessment in Physics Instruction

Assessment designed to enhance teaching and learning is called “formative assessment. ” During formative assessment, teachers and students seek information about the state of student learning and then use the acquired information to adapt teaching and learning to meet student needs. “Classroom formative assessment” (CFA) requires that teachers explicitly engage in formative assessment during classroom learning activities. At a basic level, CFA occurs naturally and is a common part of most instructional settings. Nevertheless, the systematic practice of CFA is rare in secondary and post-secondary science education. Here we provide suggestions for those interested in formative assessment for use in teaching introductory physics. A simple model of classroom formative assessment is presented. Included are examples of formative assessment activities and suggestions for implementation.
Combined effects of flow curvature and rotation on uniformly sheared turbulence

This paper describes an experiment in which a uniformly sheared turbulence was subjected to simultaneous streamwise flow curvature and rotation about the streamwise axis. The distortion of the turbulence is complex but well defined and may serve as a test case for turbulence model development. The uniformly sheared turbulence was developed in a straight wind tunnel and then passed into a curved tunnel section. At the start of the curved section the plane of the mean shear was normal to the plane of curvature so as to create a three-dimensional or ‘out of plane’ curvature configuration. On entering the curved tunnel, the flow developed a streamwise mean vorticity that rotated the mean shear about the tunnel centreline through approximately 70°, so that the shear was nearly in the plane of curvature and oriented so as to have a stabilizing effect on the turbulence. Hot wire measurements of the mean velocity, mean vorticity, mean rate of strain and Reynolds stress anisotropy development along the wind tunnel centreline are reported. The observed effect of the mean shear rotation on the turbulence was to diminish the shear stress in the plane normal to the plane of curvature while generating non-zero values of the shear stress in the plane of curvature. A rotating frame was identified for which the measured mean velocity field took the form of a simple shear flow. The turbulence anisotropy was transformed to this frame to estimate the effects of frame rotation on the structure of sheared turbulence.
Young Stellar Objects in the Large Magellanic Cloud: N63 and N180 H II Regions

We used Spitzer infrared observations to find the young stars of two H II regions in the Large Magellanic Cloud, N63 and N180. The young stellar object (YSO) candidates were identified in each nebula by means of color-color, color-magnitude diagrams, and the shapes of their spectral energy distributions (SEDs). The most luminous YSOs are found near the ionization fronts within strong 8 μm emission clumps. Most YSOs, less luminous, are seen in projection inside the H II regions. HST images show several Class I stars that have emerged along the borders of the H II regions; other YSOs are embedded in cometary clouds. The most luminous YSO of N63 is connected to a string of pointlike sources. Its SED can be modeled by a central source of stellar mass M⋆ between 7 and 11 M☉, with a circumstellar disk of outer radius Rd of ~55 AU, and an envelope of moderate accretion rate, of ~2 × 10−5 M☉ yr−1. N180 is experiencing a phase of star formation more intense than N63, attested by the properties of its most luminous YSO: M⋆ of 25 M☉, Rd of ~200 AU, and of ~1.5 × 10−3 M☉ yr−1. The modes of triggered star formation in N63 and N180 appear similar to those seen in Galactic H II regions.
EFFECT OF FREE-STREAM TURBULENCE ON SEPARATED-REATTACHING FLOWS FOR DIFFERENT ANGLES OF SEPARATION

Effects of a free-stream turbulence on a series of two-dimensional separation-reattaching flows (separation bubbles) were investigated experimentally in a low-speed wind tunnel. Models tested were two-dimensional triangular cylinders with a tail plate. Some important properties of the separation bubbles were measured with a split-film sensor driven by constant -temperature hot-wire anemometers. The effect of the turbulence on the reattachment length XR was found not to be uniform with respect to the separation angle. Large-scale vortices were formed by coalescence in the reattaching zone of the shear layer and were shed downstream with a non-dimensional frequency 0.65 ×(free-stream velocity) /XR, which was the same for all the combinations of the separation angle and the free-stream turbulence employed in this study. Geometry of the separated shear layer suggested that the large-scale vortices in the reattaching zone became flatter as XR increased.
Patterns of Helicity in Solar Active Regions

Using 46 vector magnetograms from the Stokes Polarimeter of Mees Solar Observatory (MSO), we studied patterns of local helicity in three diverse solar active regions. From these magnetograms we computed maps of the local helicity parameter alpha = J(sub z)/B(sub z). Although such maps are noisy, we found patterns at the level approximately 2 to 3 sigma(sub J(sub z)), which repeat in successive magnetograms for up to several days. Typically, the alpha maps of any given active region contain identifiable patches with both positive and negative values of alpha. Even within a single sunspot complex, several such alpha patches can often be seen. We followed 68 alpha patches that could be identified on at least two successive alpha maps. We found that the persistence fraction of such patches decrease exponentially, with a characteristic time approximately 27 hr.
Identification of space-dependent permeability in nonlinear diffusion equation from interior measurements using wavelet multiscale method

Numerical identification of the space-dependent permeability function in a nonlinear diffusion equation is considered. This problem plays an important role in promoting the permeability estimation within multiphase porous media flow. The forward problem is discretized using finite-difference methods and the identification is formulated as a minimization problem with regularization terms. To overcome disturbance of local minimum, a wavelet multiscale method is applied to solve this inverse problem. This method works by decomposing the inverse problem into multiple scales using wavelet transform so that the original inverse problem is reformulated to be a sequence of subinverse problems relying on scale variables, and successively solving these subinverse problems according to the size of scale from the longest to the shortest. The stable and fast regularized Gauss–Newton method is applied to each scale. Numerical simulations show the wide convergence, computational efficiency, anti-noise and de-noising abilities of the proposed algorithm.
The Shape of the Inverse Scree Test for Cluster Analysis

A Monte Carlo study to determine the shape of the Inverse Scree test with various numbers of true groups and under different conditions of both distribution shape and sample size. Six distributions of 3000 computer "subjects" each and a seventh (Low N) distribution of 1500 computer "subjects" were created using a random number generator. Fifty Ward hierarchical cluster analyses were completed on each distribution and medians and 96% confidence intervals were computed for clustering steps 1 through 8. The results indicated that the graphic Inverse Scree test may be distribution-independent, N-independent, and modestly curvilinear. Inferences for additional studies and guidelines for Scree analysts were presented.
Large-mode-area Bragg fiber with microstructured core for suppression of high-order modes

Photonic bandgap Bragg fibers are promising for designing large-mode-area structures owing to their high bend immunity. However, at a large core diameter, filtering of high-order modes (mainly, the LP11 mode) becomes difficult, because the propagation constant of such modes is close to that of the fundamental LP01 mode. In this paper, we demonstrate the possibility to suppress high-order modes in Bragg fibers by introducing low-index inclusions into the Bragg fiber core. Numerical analysis shows that an appropriate choice of the position and types of such inclusions allows one to increase the LP11 mode radiation loss without increasing the optical loss of the fundamental LP01 mode. The Bragg fiber with two B-doped and two F-doped rods in the core was fabricated and studied. The fundamental LP01 mode at 1064 nm had a mode-field area of about 340μm2 and an optical loss below 0.2 dB/m at a bending radius of 15 cm. The LP11 mode was not observed in both bent and straight fibers at this wavelength. Only the LP21 mode was detected in a straight fiber; however, it was completely suppressed after propagating a length of 60 cm in a fiber bent with a radius <50 cm.
Synthesis of high-purity samples of CrO2 by a simple route

Practical applications of the spintronic material CrO2 have been limited, primarily because of the difficulty in its synthesis, as it is not known to form in ambient pressures in a pure form. Here we show that CrO2 can be prepared by a simple route that bypasses the need to either apply any external pressure or measure and control it during synthesis. These samples not only exhibit saturation magnetization (MS) values close to the theoretical predicted one, but also exhibit a substantially enhanced grain size, at least an order of magnitude larger as compared to that reported prior to this work. In addition, the method provides some easy steps to tune the grain size and grain boundary density, thus enabling an investigation of this technologically important material in hitherto unexplored microstructural regimes.
Conditioning of collocation matrices and discrete Green's functions

The conditioning of spline collocation matrices is considered in the case of a boundary value problem for an mth order equation. For bases with continuity built in (which corresponds to most current implementations of splines for solving ODEs), the collocation matrix A is related to the corresponding multiple shooting matrix for a first order system. This gives the explicit form for $A^{ - 1} $ as a discrete Green function. We briefly discuss the implications for mesh selection and how our results relate to previous ones for finite differences.
On a class of branching processes on a lattice with interactions

This paper summarizes some of the results we have recently obtained for a class of branching processes on a lattice with interactions (an extended version of this, containing additional results and complete proofs, will be published elsewhere). A branching process with interactions (BPI) is a spread process in the đ-dimensional square lattice Zđ (đ≥1) consisting of points (“sites”) x=(x1,.,xđ) where each component xi is an integer. Each site may or may not be occupied by a particle (all particles being of the same type). Hence the state in which such a process is at time t≥0 is uniquely determined by the set ξt of sites which are occupied at time t. Let Ξ denote the family of all subsets of zđ, which are called configurations. (Interpretation: Site x is occupied (“infected”) in ξ∈Ξ if x∈ξ, and vacant (not infected) otherwise. ) Let us put ΞO={ξ|ξ∈Ξ, O<|ξ|<∞} and Ξ1 = {ξ|ξ∈Ξ, ξ≠O} (if B is any set, we denote its cardinality by |B|).
Nongeostrophic baroclinic instability in a two-fluid layer rotating system

Abstract The interfacial stability of two differentially rotating fluid layers in a tall, right circular cylinder is investigated analytically and experimentally. The differential speeds are such that the Ekman and Rossby numbers of the flow are small. A linearized stability analysis, including interfacial tension and viscous effects at the interface and end caps is performed on the nongeostrophic equations of motion. The nongeostrophic nature of the perturbed flow is due to the large height to radius ratio of the cylinder. The results yield stability boundaries which can be compared to quasi-geostrophic predictions for the same system. The nongeostrophic effects are found to stabilize the flow relative to the quasi-geostrophic predictions with the exception of narrow regions or “spikes” of instability in parameter space which are not accounted for by the quasi-geostrophic equations. Experiments are conducted in which stability boundaries corresponding to wavenumbers n = 1 and n = 2 are determined. Good a.
Far field patterns and inverse scattering problems for imperfectly conducting obstacles

Abstract We first examine the class of far field patterns for the scalar Helmholtz equation in ℝ2 corresponding to incident time harmonic plane waves subject to an impedance boundary condition where the impedance is piecewise constant with respect to the incident direction and continuous with respect to x ε ∂ D where ∂ D is the scattering obstacle. We then examine the class of far field patterns for Maxwell's equations in subject to an impedance boundary condition with constant impedance. The results obtained are used to derive optimization algorithms for solving the inverse scattering problem.
Levene type tests for the ratio of two scales

Tests for the equality of variances are of interest in many areas such as quality control, agricultural production systems, experimental education, pharmacology, biology, as well as a preliminary to the analysis of variance, dose–response modelling or discriminant analysis. The literature is vast. Traditional non-parametric tests are due to Mood, Miller and Ansari–Bradley. A test which usually stands out in terms of power and robustness against non-normality is the W50 Brown and Forsythe [Robust tests for the equality of variances, J. Am. Stat. Assoc. 69 (1974), pp. 364–367] modification of the Levene test [Robust tests for equality of variances, in Contributions to Probability and Statistics, I. Olkin, ed., Stanford University Press, Stanford, 1960, pp. 278–292]. This paper deals with the two-sample scale problem and in particular with Levene type tests. We consider 10 Levene type tests: the W50, the M50 and L50 tests [G. Pan, On a Levene type test for equality of two variances, J. Stat. Comput. Simul. 63 (1999), pp. 59–71], the R-test [R.G. O'Brien, A general ANOVA method for robust tests of additive models for variances, J. Am. Stat. Assoc. 74 (1979), pp. 877–880], as well as the bootstrap and permutation versions of the W50, L50 and R tests. We consider also the F-test, the modified Fligner and Killeen [Distribution-free two-sample tests for scale, J. Am. Stat. Assoc. 71 (1976), pp. 210–213] test, an adaptive test due to Hall and Padmanabhan [Adaptive inference for the two-sample scale problem, Technometrics 23 (1997), pp. 351–361] and the two tests due to Shoemaker [Tests for differences in dispersion based on quantiles, Am. Stat. 49(2) (1995), pp. 179–182; Interquantile tests for dispersion in skewed distributions, Commun. Stat. Simul. Comput. 28 (1999), pp. 189–205]. The aim is to identify the effective methods for detecting scale differences. Our study is different with respect to the other ones since it is focused on resampling versions of the Levene type tests, and many tests considered here have not ever been proposed and/or compared. The computationally simplest test found robust is W50. Higher power, while preserving robustness, is achieved by considering the resampling version of Levene type tests like the permutation R-test (recommended for normal- and light-tailed distributions) and the bootstrap L50 test (recommended for heavy-tailed and skewed distributions). Among non-Levene type tests, the best one is the adaptive test due to Hall and Padmanabhan.
THE LICK/SDSS LIBRARY. II. [Ca/Fe] AND [Mg/Fe] IN F, G, AND K STARS FROM SDSS-DR7

We analyzed the spectra of 17,600 F, G, and K stars extracted from the seventh Sloan Digital Sky Survey Data Release (SDSS-DR7) database in order to derive 〈[α/Fe]〉, [Ca/Fe], and [Mg/Fe] ratios. Particular attention has been devoted to estimating homogeneous and self-consistent atmospheric parameter values, Teff, log g, and [Fe/H], by comparing synthetic and observational Lick/SDSS indices. We present results for the sub-sample of more than 4000 spectra whose overall quality allowed us to derive fairly accurate stellar atmospheric parameter values and, therefore, reliable abundance ratios. A Monte Carlo approach was adopted to evaluate both the errors in the observational Lick/SDSS indices and in the derived parameter estimates. The analysis of the trends of [Ca/Fe] and [Mg/Fe] versus [Fe/H] pointed out that (1) the [Ca/Fe] and [Mg/Fe] ratios increase with decreasing [Fe/H] with different slopes reaching maximum average levels of +0.25 and +0.40 dex at [Fe/H] ≃ −1.75, respectively; (2) our sample contains, at a given [Fe/H], stars characterized by significantly different amounts of α-enhancement, thus belonging to different Galactic populations; and (3) the analyzed sample shows a predominance of thick disk stars for [Fe/H] > − 0.5 and the presence of stars belonging to the “high-α” halo population for −2.0 < [Fe/H] <−0.5.
Resolving the Mixed Models Controversy

Abstract Two standard mixed models with interactions are discussed. When each is viewed in the context of superpopulation models, the mixed models controversy is resolved. The tests suggested by the expected mean squares under the constrained-parameters model are correct for testing the main effects and interactions under both the unconstrained-and constrained-parameters models.
Scale Effects on Exciton Localization and Nonradiative Processes in GaN/AlGaN Quantum Wells

Previous experimental studies have allowed us to observe peculiar localization effects of excitons in GaN/AlGaN quantum wells grown by MBE, as well as efficient nonradiative inter-well carrier transfers. In this work, we use the envelope-function approximation to calculate exciton energies and wave functions. We show that the typical spatial extension of the electron and hole can by itself explain the localization and transfer processes, mainly because, due to its large effective mass, the in-plane extension of the hole is smaller than the average distance between two aluminum atoms in the barriers.
A new quotidian equation of state (QEOS) for hot dense matter

The quotidian equation of state (QEOS) is a general‐purpose equation of state model for use in hydrodynamic simulation of high‐pressure phenomena. Electronic properties are obtained from a modified Thomas–Fermi statistical model, while ion thermal motion is described by a multiphase equation of state combining Debye, Gruneisen, Lindemann, and fluid‐scaling laws. The theory gives smooth and usable predictions for ionization state, pressure, energy, entropy, and Helmholtz free energy. When necessary, the results may be modified by a temperature‐dependent pressure multiplier which greatly extends the class of materials that can be treated with reasonable accuracy. In this paper a comprehensive evaluation of the resulting thermodynamic data is given including comparison with other theories and shock‐wave data.
Microstructural Randomness Versus Representative Volume Element in Thermomechanics

Continuum thermomechanics hinges on the concept of a representative volume element (RVE), which is well defined in two situations only: (i) unit cell in a periodic microstructure, and (ii) statistically representative volume containing a very large (mathematically infinite) set of microscale elements (e.g., grains). Response of finite domains of material, however, displays statistical scatter and is dependent on the scale and boundary conditions. In order to accomplish stochastic homogenization of material response, scale-dependent hierarchies of bounds are extended to dissipative/irreversible phenomena within the framework of thermomechanics with internal variables. In particular, the free-energy function and the dissipation function become stochastic functionals whose scatter tends to decrease to zero as the material volume is increased. These functionals are linked to their duals via Legendre transforms either in the spaces of ensemble average velocities or ensemble-average dissipative forces. In the limit of infinite volumes (RVE limit (ii) above) all the functionals become deterministic, and classical Legendre transforms of deterministic thermomechanics hold. As an application, stochastic continuum damage mechanics of elastic-brittle solids is developed. ©2002 ASME
The Demand for Gasoline in China: A Cointegration Analysis

The economic reforms in China since 1979 and consequent increases in disposable income have caused total gasoline consumption to soar nearly 240% between 1980 and 1999. As the growth rate of gasoline consumption is expected to be high due to the increased economic activity resulting from China's re-accession to the WTO, the government must understand the implications for economic growth and balance of payments. Using cointegration techniques, it was found that, between 1980 and 1999, demand for gasoline was relatively inelastic to price changes, both in the short and long terms. The long-run income elasticity was 0.97, implying that the future growth rate of gasoline consumption will be close to the growth rate of the economy, which is predicted to be about 7% per annum from 2001 to 2005, and 5-6% over the decade thereafter.