Miracle-dz/UniFAR-FTUs huggingface dataset:
Pre-service Secondary Mathematics Teachers’ Beliefs about the Nature of Technology in the Classroom

This study investigated pre-service secondary mathematics teachers’ (PSTs) beliefs about teaching mathematics with technology, the experiences in which those beliefs were grounded, and the organizational structure of those beliefs. In particular, this article reports on research that was designed to investigate questions beyond that of whether technology can profitably be used before mathematical content has been mastered (the question about technology most commonly reported in the literature). Beliefs were defined as dispositions to act and were viewed through what is referred to as the sensible system framework. Through the qualitative research methodology called grounded theory, four PSTs were purposefully selected and studied. The primary dimensions of the PSTs’ core beliefs with respect to technology, referred to as their beliefs about the nature of technology in the classroom, were beliefs about the availability of technology, about the purposeful use of technology, and about the importance of teacher knowledge of technology. RésuméCette étude porte sur les idées préconçues des futurs enseignants des mathématiques au secondaire quant à l’enseignement des mathématiques par le moyen des technologies, les expériences sur lesquelles ces idées se fondent et le système grâce auquel ces idées sont maintenues. En particulier, nous analysons les résultats de recherches réalisées dans le but d’aller au-delà des idées les plus courantes dans la littérature sur les technologies, à savoir si les technologies peuvent être utilisées de façon profitable avant que les contenus mathématiques aient été maîtrisés. Ces idées ont été définies comme une disposition à agir, et sont étudiées dans un cadre que nous appelons système sensé. Au moyen d’une méthodologie de recherche qualitative appelée théorie fondée, quatre futurs enseignants ont été choisis comme objet de notre étude. Les principales dimensions des idées fondamentales de ces futurs enseignants sur les technologies, que nous avons appelées idées sur la nature des technologies dans la salle de classe, portaient sur la disponibilité des technologies, leurs différentes utilisations pratiques ainsi que l’importance des connaissances qu’en ont les enseignants.
Numerical studies of the stability of inviscid stratified shear flows

The infinitesimal stability of inviscid, parallel, stratified shear flows to two-dimensional disturbances is described by the Taylor-Goldstein equation. Instability can only occur when the Richardson number is less than 1/4 somewhere in the flow. We consider cases where the Richardson number is everywhere non- negative. The eigenvalue problem is expressed in terms of four parameters, J a ‘typical’ Richardson number, α the (real) wavenumber and c the complex phase speed of the disturbance. Two computer programs are developed to integrate the stability equation and to solve for eigenvalues: the first finds c given α and J, the second finds α and J when c ≡ 0 (i.e. it computes the stationary neutral curve for the flow). This is sometimes, but not always, the stability boundary in the α, J plane. The second program works only for cases where the velocity and density profiles are antisymmetric about the velocity inflexion point. By means of these two programs, several configurations of velocity and density have been investigated, both of the free-shear-layer type and the jet type. Calculations of temporal growth rates for particular profiles have been made.
Some integer-valued trigonometric sums

It is shown that for m = 1,2,3,…, the trigonometric sums and can be represented as integer-valued polynomials in n of degrees 2m – 1 and 2m, respectively. Properties of these polynomials are discussed, and recurrence relations for the coefficients are obtained. The proofs of the results depend on the representations of particular polynomials of degree n – 1 or less as their own Lagrange interpolation polynomials based on the zeros of the nth Chebyshev polynomial Tn(x) = cos(narccos x), -1≤x≤1.
Luminous clusters of Wolf-Rayet stars in the SBmIII galaxy NGC 4214

Discovery of strong, broad emission lines attributed to Wolf-Rayet (W-R) stars in spectra of several bright knots in the nearby Magellanic irregular galaxy NGC 4214 is presented. The shape of the broad blend at 4660 A shows that WC stars must be present, in addition to the generally more prevalent WN stars. This is consistent with the relatively high metallicity of NGC 4214 in comparison with most other W-R galaxies. Broad Hα emission, probably produced by late WN stars, is visible in the brightest knot; it serves as a warning that such a feature is not always an indication of Seyfert activity
The lobe structure of giant hailstones

Photographs of thin sections through five giant hailstones are presented to portray their bubble and crystal structures. These are interpreted to show that the hailstones grew as three-dimensional arrays of more or less completely frozen lobes, sometimes but not always separated by regions of spongy ice characterized by radial lines of bubbles. Some lobes contained regularly spaced hyperfine growth layers consisting of series of concentric bubble fronts a few hundred microns apart. These layers are interpreted as being due to fluctuations in growth rate associated with the tumbling of the hailstones. The growing surfaces of the lobes were strongly convex outward. This caused successive growth layers to become convoluted or scalloped. When the surface of a whole hailstone was viewed it sometimes created the false impression that the stone was an aggregate of much smaller hailstones. The presence of surface knobs associated with the lobes significantly enhances the efficiency of heat loss from the hailstone surface. Such an effect is important in that it reduces the proportion of unfrozen water incorporated within a rapidly growing hailstone. There is even some evidence that a giant 8 cm diameter hailstone can grow in this way without becoming appreciably spongy.
Stimulated Brillouin scattering of a KrF laser

A series of experiments in which the efficiency and fidelity of SBS (stimulated Brillouin scattering) wavefront reconstruction are measured as a function of the temporal coherence, focusing geometry, and power of the laser source is described. The primary motivation of the research is to assess the potential of SBS as the basis of a high-resolution image protection system. Thus, a series of high-resolution image projection experiments using a SBS mirror is also described. It is shown that provided that the coherent length of the laser is longer than the active focal region primarily responsible for the growth of the SBS wave, high SBS reflectivities can be obtained which are independent of the Rayleigh range of the focusing system used. In addition, wavefront reconstruction fidelities having values approaching unity can be observed when using laser powers near the threshold for the SBS process. >
DETONATION CELL SIZES - A NUMERICAL STUDY

Experiments have shown that many relevant features characterizing detonation propagation can be correlated to the natural size that cells are experimentally observed to assume. But well-posedness of the cell-size concept is not so obvious from the standpoint of analysis and computational studies. It is only because of the chemical time that the problem cannot be reduced to a Riemann problem, without time or length scale; it is thus clear that any meaningful measure of the cell size is necessarily scaled by the chemical time. Still, this leaves plenty of room for discussion, and computations provide a convenient tool for further investigation. But until recently, even two-dimensional computations could only be performed in narrow domains, resulting in a cell width that adapts to the width of a domain, with, as a minimum, half a cell across the computational domain. We have now performed some wider computations, showing cells that become irregular, given enough width. There is then a range of sizes, so that the size assumed in wide domains cannot nnambiguously be used as an objective measure. Other alternate definitions, such as the minimm channel width that can support cells, all offer serious inconvenients and limitations. The only consistent way is then to define an average cell size, obtained by counting the number of irregular cells across and to divide the channel width by the number of cells. This criterion appears to yield consistent results. Finally, a grid resolution analysis shows that these results and conclusions remain unchanged as the grid is refined.
Vector order-statistics for impulse detection in noisy color image sequences

This paper focuses on a new three-dimensional vector filtering approach for the impulse noise suppression in noisy color image sequences. Like the vector median-based filters, the proposed method utilises a reduced ordering scheme. However, in order to approach the optimal filtering situation, when only affected samples are estimated whereas noisy image points are passed to a filter output without the change, the proposed method is controlled by the binary decision rule. As a switch between the identity filter (no filtering operation) and the vector median serves a simple comparison of the filter threshold and Euclidean distance between the central sample and the mean of several vector order-statistics with the smallest distances to the input samples. The proposed method is characterised by excellent results, especially in terms of the mean absolute error criteria.
Likelihood ratio statistics based on an integrated likelihood

An integrated likelihood depends only on the parameter of interest and the data, so it can be used as a standard likelihood function for likelihood-based inference. In this paper, the higher-order asymptotic properties of the signed integrated likelihood ratio statistic for a scalar parameter of interest are considered. These results are used to construct a modified integrated likelihood ratio statistic and to suggest a class of prior densities to use in forming the integrated likelihood. The properties of the integrated likelihood ratio statistic are compared to those of the standard likelihood ratio statistic. Several examples show that the integrated likelihood ratio statistic can be a useful alternative to the standard likelihood ratio statistic. Copyright 2010, Oxford University Press.
A consistent incompressible SPH method for internal flows with fixed and moving boundaries

An improved incompressible smoothed particle hydrodynamics (ISPH) method is presented, which employs first‐order consistent discretization schemes both for the first‐order and second‐order spatial derivatives. A recently introduced wall boundary condition is implemented in the context of ISPH method, which does not rely on using dummy particles and, as a result, can be applied more efficiently and with less computational complexity. To assess the accuracy and computational efficiency of this improved ISPH method, a number of two‐dimensional incompressible laminar internal flow benchmark problems are solved and the results are compared with available analytical solutions and numerical data. It is shown that using smaller smoothing lengths, the proposed method can provide desirable accuracies with relatively less computational cost for two‐dimensional problems. Copyright © 2015 John Wiley & Sons, Ltd.
New Monte Carlo Methods With Estimating Derivatives

Part 1 Estimation of integrals and solution of integral equations: estimation of integrals recurrent estimates of Monte Carlo method for the solution to an integral equation of the second kind variance of the basic unbiased estimate branching chains and solutions to nonlinear equations cost of various algorithms for solving integral equations solving problems with stochastic parameters. Part 2 Estimation of derivatives: vector Monte Carlo algorithms calculation derivatives and perturbations with respect to parameters calculation of parametric derivatives in a special case. Part 3 Solution of the Helmholtz equation: the "walk on spheres" process the use of probabilistic representation the use of integral representations new algorithms for variable c(r) "walk on spheres" algorithms for solving Helmholtz equation in the n-dimensional space solving difference equations by the Monte Carlo method additional remarks. Part 4 Solution of metaharmonic equations and elliptic systems. Part 5 Monte Carlo methods with calculating parametric derivatives in the radiation transport theory. Part 6 Solution of nonlinear integral equations. Appendix: Numerical simulation of random variables numerical simulation of random fields remarks about simulation algorithms with the use of multiprocessor systems. (Part contents)
Two–dimensional solidification in a corner

Analytical and numerical techniques are used to study the solidification of 1/2&pgr; and 3/2&pgr; wedges of liquid which are initially at their fusion temperature. An enthalpy method is used to obtain numerical solutions to these problems and the results are compared with asymptotic solutions for large and small Stefan numbers (the Stefan number being defined as the ratio of latent to sensible heats). The new solutions for small Stefan number are shown to provide surprisingly good approximations, especially for the 3/2&pgr; wedge. New results for heat transfer in a wedge (in the absence of a change of phase) are derived and applied in the asymptotic analysis, as are new conservation laws for the Stefan problem.
Spectroscopic survey of ASAS eclipsing variables: search for chromospherically active eclipsing binary stars – I

We have started a spectroscopic survey to identify new chromospherically active components and low-mass pre-main sequence (PMS) stars in recently discovered All Sky Automated Survey (ASAS) eclipsing binaries. In this paper, we briefly describe our scientific motivation, the observing tools and the results obtained from the first phase of this survey. Using the available observing facilities in India, the spectroscopic observations of a sample of 180 candidate eclipsing binary stars selected from ASAS-I&II releases were carried out during 2004-2006. The strength of Ha emission was used to characterize the level of chromospheric activity. Our spectroscopic survey reveals that out of 180 stars about 36 binary systems show excess Ha emission. One of the objects in our sample, ASAS 081700-4243.8, displays very strong Ha emission. Follow-up high-resolution spectroscopic observations reveal that this object is indeed very interesting and most likely a classical Be-type system with KOIII companion.
Structure of turbulent boundary layers on smooth and rough walls

The structure of turbulent boundary layers which develop with zero pressure gradient on a smooth wall and a k-type rough wall was examined using arrays of X-wires. Although the data were obtained only on two orthogonal planes, the technique provides some information on the three-dimensionality of the large-scale structures. The major effect of the roughness is to tilt the inclination of the structures towards the wall-normal direction. This is caused by the reduced damping of the wall-normal velocity fluctuations close to the rough surface and the break-up of structures whose scales are comparable to the size of the roughness elements. Both effects cause a reduction in the streamwise lengthscales, as suggested by all the measured two-point correlations. The correlations also show that the roughness tends to reduce the overall anisotropy of the large-scale motion. There is evidence to suggest that the magnitude of the vorticity field is larger over the rough wall.
Lyapunov-like techniques for stochastic stability

The purpose of this paper is to give a survey of the results proved in Florchinger (1993) concerning the stabilizability problem for control stochastic nonlinear systems driven by a Wiener process. Sufficient conditions for the existence of stabilizing feedback laws which are smooth, except possibly at the equilibrium point of the system, are provided by means of stochastic Lyapunov-like techniques. The notion of dynamic asymptotic stability in probability of control stochastic differential systems is introduced, and the stabilization by means of dynamic controllers is studied. <<ETX>>
Spontaneous emission model of surface-emitting DFB semiconductor lasers

A general spontaneous emission model is developed for surface-emitting (SE) distributed feedback (DFB) semiconductor lasers. The frequency distribution of spontaneous emission noise below lasing threshold and the spontaneous emission rate in lasing operation are formulated by using a transfer matrix method combined with the Green's function method. The effective linewidth enhancement factor is obtained from this model in terms of the elements of the transfer matrix. By way of example, the author applies the formulation to a standard SE DFB laser, and a SE lambda /4-shifted DFB laser with a distributed Bragg reflector (DBR) mirror. In particular, the author analyzes the below-threshold spectrum, the threshold current density, the differential quantum efficiency, and the spectral linewidth of these lasers. >
A theory of particle deposition in turbulent pipe flow

The paper describes a theory of particle deposition based formally on the conservation equations of particle mass and momentum. These equations are formulated in an Eulerian coordinate system and are then Reynolds averaged, a procedure which generates a number of turbulence correlations, two of which are of prime importance. One represents ‘turbulent diffusion’ and the other ‘turbophoresis’, a convective drift of particles down gradients of mean-square fluctuating velocity. Turbophoresis is not a small correction; it dominates the particle dynamic behaviour in the diffusion-impaction and inertia-moderated regimes. Adopting a simple model for the turbophoretic force, the theory is used to calculate deposition from fully developed turbulent pipe flow. Agreement with experimental measurements is good. It is found that the Saffman lift force plays an important role in the inertia-moderated regime but that the effect of gravity on deposition from vertical flows is negligible. The model also predicts an increase in particle concentration close to the wall in the diffusion-impaction regime, a result which is partially corroborated by an independent ‘direct numerical simulation’ study. The new deposition theory represents a considerable advance in physical understanding over previous free-flight theories. It also offers many avenues for future development, particularly in the simultaneous calculation of laminar (pure inertial) and turbulent particle transport in more complex two- and three-dimensional geometries.
Resonant energy absorption of rare-gas clusters in strong laser pulses

The ionization dynamics of rare-gas clusters in strong femtosecond laser pulses is studied microscopically by means of classical molecular dynamics using a hierarchical tree code. Systematic investigations for laser pulses from 25 to 400 fs duration have shown a transition from field ionization to resonant excitation of a collective motion of the cluster electrons. The latter effect is associated with a strong energy absorption and can be microscopically identified by examining the phase lag of the electron oscillation with respect to the laser field. The optimal conditions depend, via the expansion time, strongly on the cluster size, which was varied from 102 up to 104 atoms.
An observational study of an arctic front during he IPY‐THORPEX 2008 campaign

The fact that severe weather associated with polar lows and arctic fronts still comes unforeseen and puts human life at risk shows that an effort towards increased understanding of them is required. The observations of an arctic front by dropsondes and Doppler lidar carried onboard a research aircraft during the IPY‐THORPEX ﬁeld campaign offered a rare opportunity to investigate the mesoscale structure of the front and to validate the output from operational numerical weather prediction models. The observations revealed features similar to those of polar fronts such as a relatively steep frontal zone, the presence of a strong low‐level jet and an elevated dry slot, making the arctic front appear as a shallow cold front conﬁned to levels below 700 hPa. The dry slot indicated the presence of a downfolding of the tropopause, and together with the observations of an upper‐level jet this strongly supports the inclusion of an arctic tropopause fold connected to the arctic jet stream in a conceptual model of the tropopause. A comparison between data from operational numerical weather prediction models and observations obtained during the ﬂight shows that the models simulated the broad features of the frontal zone such as jets, dry slot and the depth of the front fairly well, although parts of the front were slightly misplaced. However, the models failed completely in their simulations of one of the three mesoscale cyclones associated with the front as they located it over the coast of northern Norway while the correct location was over the Greenland Sea according to the observations and analysis.
Estimating Response-Maximized Decision Rules With Applications to Breastfeeding

To estimate the sequence of actions that optimizes response in a longitudinal setting, it is important to study the actions as part of a set of decision rules rather than in a series of single-action comparisons. We take as our motivating example the estimation of the set of decision rules for the duration of breastfeeding with a view to maximizing infant growth. Breastfeeding has many well-recognized beneficial effects on health and development. However observational evidence has suggested that breastfeeding is associated with reduced infant growth, although the long-term consequences for stature and adiposity remain controversial. The Promotion of Breastfeeding Intervention Trial (PROBIT) recruited 17,046 women in which hospitals and their affiliated polyclinics in Belarus were randomized to a breastfeeding promotion intervention or to standard care. In this article, we propose Structural Mean Models and estimate their parameters using G-estimation to obtain unbiased estimates of the effect of continued breastfeeding on infant growth (weight or length) at one year of age. We also implement a modified version of the G-estimation algorithm that is asymptotically unbiased; this is the first real-data application of the algorithm. Finally, we compare the decision rules implied by the G-estimates with the decision implied by a myopic optimization estimation approach, that is, we compare with decision rules that maximize response in the short-term. The breastfeeding regimes selected by each of the three models are optimal in the sense that specific criteria were optimized; the criteria considered here (maximizing weight or length) were chosen for simplicity, but may not lead to better overall health. We demonstrate in the context of a breastfeeding promotion intervention trial that optimal myopic decision strategies do not coincide with strategies that optimize a longer-term response. Please see the online supplements for a correction to this article.
Determination of forces and linearized parameters of radial active magnetic bearings by finite element technique

Load capacity is a primary performance criterion of an active magnetic bearing (AMB) system. The load capacity depends on the size and geometry of the bearings as well as on the performance of the control system. In this paper, we use a nonlinear two-dimensional (2-D) finite element method (FEM) to predict the performance of radial magnetic bearings. The force calculations based on the finite element method are verified by measurements with two machines equipped with active magnetic bearings. The parameters of a linearized model of radial bearings are also calculated at different operation points. With this information, the load capacity can be estimated.