Miracle-dz/UniFAR-FTUs huggingface dataset:
Aharonov-Bohm effect in normal metal quantum coherence and transport

Abstract We review some of the recent surprising theoretical and experimental results obtained on the transport properties of small disordered metal samples. Even in the presence of disorder, the quantum mechanical interference of electron wavefunctions can still be observed. The Aharonov-Bohm effect is a particularly clear demonstration of this. In doubly connected structures (such as loops of wire) threaded by a magnetic flux, the electrical conductance oscillates because of the Aharonov-Bohm effect. In fact, because the electron trajectories are diffusive (i.e. random walks), even a lone wire (a singly connected structure) will exhibit a random pattern of conductance fluctuations as a function of the magnetic field because of the same interference effects. All that is required for the observation of these interferences is that the electrons retain ‘phase memory’ duing the period of transit through the sample. The length over which memory is maintained (the phase coherence length) can be much larger tha.
Multifunctional microscope for far-field and tip-enhanced Raman spectroscopy

The development of a versatile and easy-to-use instrument designed for Raman micro- and nanospectroscopy in the visible range is described in this work. An atomic force microscope, an inverted confocal microscope, and a piezostage are combined to perform an accurate and fast tip-laser alignment and to characterize large areas under the same conditions of illumination across the surface. In addition, a metallized tip is used to locally enhance the electromagnetic field and to probe the sample surface leading to in situ chemical analysis at the nanoscale. Both far-field and tip-enhanced Raman spectroscopies (TERS) have been carried out on dye molecules and on nano-objects with short exposure times. The TERS observation of tip-induced sample deformation on single-walled carbon nanotubes is also presented.
On the Dynamics of Concentric Eyewall Genesis: Space–Time Empirical Normal Modes Diagnosis

Abstract A novel statistical technique called space–time empirical normal mode (ST-ENM) is applied in a diagnostic study of the genesis of a secondary eyewall in a simulated hurricane using the nonhydrostatic, high-resolution fifth-generation Pennsylvania State University (PSU)–National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5). The bases obtained from the ST-ENM technique are nonstationary, dynamically relevant, and orthogonal in the sense of wave activity. The wave activity spectra of the wavenumber-1 anomalies show that the leading modes (1–6) exhibit mainly characteristics of vortex Rossby waves (VRWs). These modes together explain about 75% of the total wavenumber-1 variance in a period of 24 h. Analysis of the Eliassen–Palm (EP) flux and its time-mean divergence corresponding to the total contribution from these modes indicated that in the lower troposphere VRWs not only propagate inward (outward) in the primary eyewall region where the radial gradient of the basic-state potential.
Numerical simulation of mammatus.

Abstract Mammatus are hanging lobes on the underside of clouds. Although many different mechanisms have been proposed for their formation, none have been rigorously tested. In this study, three-dimensional numerical simulations of mammatus on a portion of a cumulonimbus cirruslike anvil are performed to explore some of the dynamic and microphysical factors that affect mammatus formation and evolution. Initial conditions for the simulations are derived from observed thermodynamic soundings. Five observed soundings are chosen—four were associated with visually observed mammatus and one was not. Initial microphysical conditions in the simulations are consistent with in situ observations of cumulonimbus anvil and mammatus. Mammatus form in the four model simulations initialized with the soundings for which mammatus were observed, whereas mammatus do not form in the model simulation initialized with the no-mammatus sounding. Characteristics of the modeled mammatus compare favorably to previously published mamm.
The five exceptional simple Lie superalgebras of vector fields

The five simple exceptional complex Lie superalgbras of vector fields are described. One of them is new; the other four are explicitely described for the first time. All of the exceptional Lie superalgebras are obtained with the help of the Cartan prolongation or a generalized prolongation. The description of several of the exceptional Lie superalgebras is associated with the Lie superalgebra AS - the nontrivial central extension of the supertraceless subalgebra SPE(4) of the periplectic Lie superalgebra PE(4) that preserves the nondegenerate odd bilinear form on the (4|4)-dimensional superspace. (A nontrivial central extension of SPE(n) only exists for n=4. )
Concavity and B‐Concavity of Solutions of Quasilinear Filtration Equations

Spatial concavity properties of non‐negative weak solutions of the filtration equations with absorption ut = (φ(u))xx−ψ(u) in Q = R×(0, ∞), φ′⩾0, ψ⩾0 are studied. Under certain assumptions on the coefficients φ, ψ it is proved that concavity of the pressure function is a consequence of a ‘weak’ convexity of travelling‐wave solutions of the form V(x, t) = θ(x−λt+a). It is established that the global structure of a so‐called proper set B = {V} of such particular solutions determines a property of B‐concavity for more general solutions which is preserved in time. For the filtration equation ut = (φ(u))xx a semiconcavity estimate for the pressure, vxx⩽(t+τ)−1θ″(ξ), due to the B‐concavity of the solution to the subset B of the explicit self‐similar solutions θ(x/√t+τ)) is proved.
Magnetic flux loss from interstellar clouds

Une etude des densites de differentes particules chargees dans l'equilibre ionisation-recombinaison et de la dissipation du champ magnetique dans les nuages interstellaires est realisee avec de nouveaux coefficients de taux de reaction. L'echelle de temps de la perte de flux magnetique est analysee
Resources for Refining Mathematical Conceptions: Case Studies in Learning About Linear Functions

In this article, I describe the refinement of a conception in the domain of linear functions, the use of the x-intercept in equations of the form y = mx + b, to illustrate the resources used by students to refine a conception. The examples presented show how students refined their use of the x-intercept by (a) narrowing the problem contexts in which they applied this conception, (b) making connections between conceptions, (c) using a mathematical procedure, and (d) refining their verbal descriptions of how the graph of a line changes as a result of a change in the equation. The analysis draws on diSessa's (1993) theory of science learning and the recommendations made by Smith, diSessa, and Roschelle (1993) for describing conceptual change. The results extend this prior work from science to mathematics and identify resources used by students that teachers can draw on to support the learning of mathematical concepts.
Resistive switching in hafnium dioxide layers: Local phenomenon at grain boundaries

Overcoming challenges associated with implementation of resistive random access memory technology for non-volatile information storage requires identifying the material characteristics responsible for resistive switching. In order to connect the switching phenomenon to the nano-scale morphological features of the dielectrics employed in memory cells, we applied the enhanced conductive atomic force microscopy technique for in situ analysis of the simultaneously collected electrical and topographical data on HfO2 stacks of various degrees of crystallinity. We demonstrate that the resistive switching is a local phenomenon associated with the formation of a conductive filament with a sufficiently small cross-section, which is determined by the maximum passing current. Switchable filament is found to be formed at the dielectric sites where the forming voltages were sufficiently small, which, in the case of the stoichiometric HfO2, is observed exclusively at the grain boundary regions representing low resistant.
Generalized Non-Parametric Deconvolution with an Application to Earnings Dynamics

In this paper,we construct a nonparametric estimator of the distributions of latent factors in linear independent multi-factor models under the assumption that factor loadings are known. Our approach allows to estimate the distributions of up to L(L+1)/2 factors given L measurements. The estimator works through empirical characteristic functions. We show that it is consistent, and derive asymptotic convergence rates. Monte-Carlo simulations show good finite-sample performance, less so if distributions are highly skewed or leptokurtic. We finally apply the generalized deconvolution procedure to decompose individual log earnings from the PSID into permanent and transitory components.
ORDER CONVOLUTION AND VECTOR-VALUED MULTIPLIERS

Let I = (0,1) with the usual topology. For x, y 2 I, we define xy = max(x, y). Then I becomes a locally compact commutative topological semigroup. The Banach space L 1 (I) of all Lebesgue integrable functions on I becomes a commutative semisimple Banach algebra with order convolution as multiplication. A bounded linear operator T on L 1 (I) is called a multiplier of L 1 (I) if T(f ⋆ g) = f ⋆ T g for all f, g 2 L 1 (I). The space of multipliers of L 1 (I) was determined by Johnson and Lahr. Let X be a Banach space and L 1 (I, X) be the Banach space of all X-valued Bochner integrable functions on I. We show that L 1 (I, X) becomes an L 1 (I)-Banach module. Suppose X and Y are Banach spaces. A bounded linear operator T from L 1 (I, X) to L 1 (I, Y ) is called a multiplier if T(f ⋆ g) = f ⋆ T g for all f 2 L 1 (I) and g 2 L 1 (I, X). In this paper, we characterize the multipliers from L 1 (I, X) to L 1 (I, Y ).
The age-metallicity relationship for the clusters of the Large Magellanic Cloud.

Moderate dispersion spectrophotometric scans with the intensified Reticon array constructed by S. Shectman have been obtained using the du Pont telescope of the Las Campanas Observatory for 38 stars expected to be members of 15 clusters in the Large Magellanic Cloud. Ages for these clusters are deduced from a transformation of their classification in the scheme of Searle, Wilkinson, and Bagnuolo. Abundances are derived from the scans using a crude analysis applied to computer-generated pseudoequivalent widths calibrated by identical observations of 42 stars in six galactic globular clusters and by several galactic supergiants. A strong age-metallicity relationship is found and the chemical history of the LMC is discussed. Unlike the solar neighborhood or galactic halo, simple models of chemical evolution are adequate to fit our derived age-abundance correlation.
VARIATIONAL HOMOTOPY PERTURBATION METHOD FOR SOLVING THE NONLINEAR GAS DYNAMICS EQUATION

A. Noor et al. [7] analyze a technique by combining the variational iteration method and the homotopy perturbation method which is called the variational homotopy perturbation method (VHPM) for solving higher dimensional initial boundary value problems. In this paper, we consider the VHPM to obtain exact solution to Gas Dynamics equation.
Plasma diagnostic tools for optimizing negative hydrogen ion sources

The powerful diagnostic tool of optical emission spectroscopy is used to measure the plasma parameters in negative hydrogen ion sources based on the surface mechanism. Results for electron temperature, electron density, atomic-to-molecular hydrogen density ratio, and gas temperature are presented for two types of sources, a rf source and an arc source, which are currently under development for a neutral beam heating system of ITER. The amount of cesium in the plasma volume is obtained from cesium radiation: the Cs neutral density is five to ten orders of magnitude lower than the hydrogen density and the Cs ion density is two to three orders of magnitude lower than the electron density in front of the grid. It is shown that monitoring of cesium lines is very useful for monitoring the cesium balance in the source. From a line-ratio method negative ion densities are determined. In a well-conditioned source the negative ion density is of the same order of magnitude as the electron density and correlates with .
Multiplicity scaling of target protons in high-energy nucleus-nucleus and hadron-nucleus interactions

Multiplicity scaling of target protons emitted from nucleus? nucleus (16O? AgBr interactions at 2.1 AGeV and 32S? AgBr interactions at 200 AGeV), pion? nucleus (? AgBr interactions at 350 GeV/c) and proton? nucleus interactions (p? AgBr interactions at 200 GeV/c) has been investigated. The experimental points are found to lie approximately on the curve described by ? (z) = Azexp? ( ? Bz) with A = 3.36 ? 0.19 and B = 1.74 ? 0.06 for all the four interactions. A comparison of the fit with the function ? (z) = (Az + Bz3 + Cz5 + Dz7)exp? ( ? Ez) has also been performed.
A primal-dual consensus algorithm for convex problems from network control and estimation*

Abstract In this paper we propose a distributed algorithm for solving separable convex optimization problems on graphs arising for example from estimation and control in networks. We derive a primal-dual decomposition algorithm for solving this type of separable optimization problems in a distributed fashion given restrictions on the communication topology. The proposed algorithm is based on consensus principles in combination with local subgradient updates for the primal-dual variables. The main novelty of our algorithm consists in the way the weights in the consensus process are updated using arguments from optimization theory, while in most of the existing distributed algorithms based on consensus principles the weights have to be tuned.
Microwave Imaging of Immersed Dielectric Bodies: An Experimental Survey

Abstract Diffraction tomography provides a good method for reconstructing cross-section images of weakly scattering dielectric objects. The Born and Rytov approximations are well-known approximations for the first-order diffraction tomography method. In this paper, the restrictions of the Born and Rytov approximations are experimentally investigated when the object is immersed in a medium. Microwave tomography images of several kinds of dielectrics of different shapes and dielectric constants are imaged both in the air and in the sand. It is shown experimentally from the resultant images that the Born approximation produces a better estimation for objects small in size and even for objects of large deviations in relative refractive index; on the other hand, Rytov approximation gives a more accurate estimation mainly for objects with small deviations in relative refractive index. The Rytov approximation is also valid for large-sized objects if the first condition is satisfied. The results also show that it is possible to image objects located in medium by the diffraction tomography method and that the method can be applied in biomedical and NDT applications.
Two‐scale models for rough surface scattering: Comparison between the boundary perturbation method and the integral equation method

This paper presents a comparison between two models for rough surface scattering computations: the boundary perturbation method (BPM) and the integral equation method (IEM). They differ in two fundamental aspects: the method used to compute the electric and magnetic fields on the surface and the surface information required for the computation. The two approaches lead analytically to the same solution in the two asymptotic cases of very large and very small vertical displacements, with no intermediate scales. For a composite surface the solution of the BPM is expressed as the sum of two terms, while a series development up to higher orders can be formulated with the IEM. In this paper, the comparison is restricted to composite surfaces and, particularly, to the ocean surface. After presenting a method for the two‐scale decomposition of a rough surface, which satisfies the constraints of the electromagnetic model for each scale, we compute the scattering by the ocean surface using both models for various instrumental configurations and surface conditions. We show that considering the accuracy of usual radar measurements and under the assumptions made for the development of the models, both methods give very similar results. Since the BPM is based on a simple physical argument and appears to be more efficient than the two‐scale IEM with regard to the computation time, the BPM should be preferred for ocean‐like rough surfaces.
Modeling of the deformation of a liquid droplet impinging upon a flat surface

This article presents a theoretical study of the deformation of a spherical liquid droplet impinging upon a flat surface. The study accounts for the presence of surface tension during the spreading process. The theoretical model is solved numerically utilizing deforming finite elements and grid generation to simulate accurately the large deformations, as well as the domain nonuniformities characteristic of the spreading process. The results document the effects of impact velocity, droplet diameter, surface tension, and material properties on the fluid dynamics of the deforming droplet. Two liquids with markedly different thermophysical properties, water and liquid tin, are utilized in the numerical simulations because of their relevance in the industrial processes of spray cooling and spray deposition, respectively. The occurrence of droplet recoiling and mass accumulation around the splat periphery are standout features of the numerical simulations and yield a nonmonotonic dependence of the maximum splat radius on time.
Irreversible Processes in a Magnetoplasma

Magnetically confined plasmas exhibit some interesting instabilities that have somewhat bedeviled the long quest for fusion power in tokamak machines. The magnetic fields employed are strong in the sense that the parameter tu = COCT, where ω€ is the cyclotron frequency and τ is the collision interval, is a very large number. The purpose of the paper is to relate these instabilities to σ, the entropy production rate per unit volume. In a neutral gas σ is non-negative, which result can be obtained as a local form of Boltzmann's i/-theorem. With σ expanded in the Knudsen number (ε) power series, σ = σ-L + σ2 + · · ·, where σ± is the familiar, non-negative quadratic form, the secondorder term σ2 = Ο (ε), may have either sign. In the usual case, for ε smal enough, ι » \21 d th inequality σ ̂ 0 follows. However in a magnetoplasma, we shall show that σ1 = Ο(τσ~), whereas σ2 = O(tn~). This means that in tokamaks <72 (which may have either sign) dominates σχ. It is therefore possible that in some circumstances σ is negative and the outcome is an unstable fluctuation. Another way of expressing this result, is that the heat flows up the temperature gradient, albeit only for a short time. In the course of establishing this surprising result, we shall give a method of calculating σ2 that is independent of the form of Boltzmann's collision integral. Our conclusions are supported by reference to tokamak experiments.
Density Functional Theory Investigation of Bi(Ga,Al)O3Solid Solution for High-Performance Lead-Free Piezoelectric Materials

In this work, we have investigated the ferroelectric property of BiAlxGa(1−x)O3with x = 0.00, 0.25, 0.50, 0.75, and 1.00 for replacement of the widely use, PZT which is toxic. The techniques used are density functional theory with local density approximation (LDA) as well as projector augmented-wave method (PAW). The composition (x) was varied via setting the appropriated supercell. The solid solutions in both tetragonal (P4 mm) and rhombohedral (R3c) phase have been simulated to determine crystal stability, phase transition, and ferroelectric properties. From the results, the expected morphotropic phase boundaries (MPB) have not been observed because all R3c structures are more energetically stable than those of P4 mm. Therefore, Bi(Ga,Al)O3solid solution cannot display higher ferroelectricity than that of pure BiGaO3. However, the calculated polarization of Bi(Ga,Al)O3are still very high compared to other ferroelectric materials, e.g. AgNbO3and BaTiO3. This suggests that the considered solid solution could be one of lead-free candidates for future industrial applications.
Estimation of the Mean of a Sensitive Variable in the Presence of Auxiliary Information

Sousa et al. (2010) introduced a ratio estimator for the mean of a sensitive variable and showed that this estimator performs better than the ordinary mean estimator based on a randomized response technique (RRT). In this article, we introduce a regression estimator that performs better than the ratio estimator even for modest correlation between the primary and the auxiliary variables. The underlying assumption is that the primary variable is sensitive in nature but a non sensitive auxiliary variable exists that is positively correlated with the primary variable. Expressions for the Bias and MSE (Mean Square Error) are derived based on the first order of approximation. It is shown that the proposed regression estimator performs better than the ratio estimator and the ordinary RRT mean estimator (that does not utilize the auxiliary information). We also consider a generalized regression-cum-ratio estimator that has even smaller MSE. An extensive simulation study is presented to evaluate the performances of the proposed estimators in relation to other estimators in the study. The procedure is also applied to some financial data: purchase orders (a sensitive variable) and gross turnover (a non sensitive variable) in 2009 for a population of 5,336 companies in Portugal from a survey on Information and Communication Technologies (ICT) usage.
Ultraviolet Imaging Telescope observations of the Crab Nebula

We obtained ultraviolet images of the Crab Nebula with the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Space Shuttle mission in 1990 December. The UV continuum morphology of the Crab is generally similar to that in the optical region, but the wispy structures are less conspicuous in the UV and X-ray. UV lines emmission from the thermal filaments is not strong. UV spectral index maps with a resolution of 10″ show a significant gradient across the nebula, with the outer parts being redder, as expected from synchrotron losses. The location of the bluest synchrotron continuum does not coincide with the pulsar
A method of smoothed particle hydrodynamics using spheroidal kernels

We present a new method of three-dimensional smoothed particle hydrodynamics (SPH) designed to model systems dominated by deformation along a preferential axis. These systems cause severe problems for SPH codes using spherical kernels, which are best suited for modeling systems which retain rough spherical symmetry. Our method allows the smoothing length in the direction of the deformation to evolve independently of the smoothing length in the perpendicular plane, resulting in a kernel with a spheroidal shape. As a result the spatial resolution in the direction of deformation is significantly improved. As a test case we present the one-dimensional homologous collapse of a zero-temperature, uniform-density cloud, which serves to demonstrate the advantages of spheroidal kernels. We also present new results on the problem of the tidal disruption of a star by a massive black hole.