Miracle-dz/UniFAR-FTUs huggingface dataset:
Vibration of axisymmetric composite piezoelectric shells coupled with internal fluid

This paper presents the theoretical and finite element formulations of piezoelectric composite shells of revolution filled with compressible fluid. The originality of this work lies (i) in the development of a variational formulation for the fully coupled fluid/piezoelectric structure system, and (ii) in the finite element implementation of an inexpensive and accurate axisymmetric adaptive laminated conical shell element. Various modal results are presented in order to validate and illustrate the efficiency of the proposed fluid–structure finite element formulation. Copyright © 2007 John Wiley & Sons, Ltd.
KELVIN–HELMHOLTZ CREEPING FLOW AT THE INTERFACE BETWEEN TWO VISCOUS FLUIDS

The Kelvin–Helmholtz flow is a shearing instability that occurs at the interface between two fluids moving with different speeds. Here, the two fluids are each of finite depth, but are highly viscous. Consequently, their motion is caused by the horizontal speeds of the two walls above and below each fluid layer. The motion of the fluids is assumed to be governed by the Stokes approximation for slow viscous flow, and the fluid motion is thus responsible for movement of the interface between them. A linearized solution is presented, from which the decay rate and the group speed of the wave system may be obtained. The nonlinear equations are solved using a novel spectral representation for the streamfunctions in each of the two fluid layers, and the exact boundary conditions are applied at the unknown interface location. Results are presented for the wave profiles, and the behaviour of the curvature of the interface is discussed. These results are compared to the Boussinesq–Stokes approximation which is also solved by a novel spectral technique, and agreement between the results supports the numerical calculations.
Presenting the Snowflake Video Imager (SVI)

Abstract Herein the authors introduce the Snowflake Video Imager (SVI), which is a new instrument for characterizing frozen precipitation. An SVI utilizes a video camera with sufficient frame rate, pixels, and shutter speed to record thousands of snowflake images. The camera housing and lighting produce little airflow distortion, so SVI data are quite representative of natural conditions, which is important for volumetric data products such as snowflake size distributions. Long-duration, unattended operation of an SVI is feasible because datalogging software provides data compression and the hardware can operate for months in harsh winter conditions. Details of SVI hardware and field operation are given. Snowflake size distributions (SSDs) from a storm near Boulder, Colorado, are computed. An SVI is an imaging system, so SVI data can be utilized to compute diverse data products for various applications. In this paper, the authors present visualizations of frozen particles (i.e., snowflake aggregates as we.
A Comparative Study of ASOS and USCRN Temperature Measurements

Abstract Temperature measurements from the U.S. Climate Reference Network (USCRN) instrument system were compared to the Automated Surface Observing System (ASOS) ambient air temperature measurements and were examined under different regimes of wind speed and solar radiation. Influences due to observing practice differences and the effects of siting differences were discussed. This analysis indicated that the average difference between the ASOS and USCRN temperatures is on the order of 0.1°C. However, problems were noticed that were possibly related to the ASOS shield effectiveness, including a solar radiation warm effect under calm conditions and the dependence of ASOS minus USCRN temperature on wind speed. The ASOS and USCRN time of observation difference was on the order of ∼0.05°C, with a warmer ASOS daily Tmax and a cooler ASOS daily Tmin. The local effect complicates the bias analysis because it depends not only on local heating/cooling, but it can be strongly modified by cloudiness, wind, and solar.
Wavefront folding, chaos, and diffraction for sound propagation through ocean internal waves

This work presents an analysis of the effects of ocean internal waves on long-range acoustic pulse propagation from the geometrical-optics point of view. The chaotic behavior of rays and the microfolding of timefronts are investigated. The extent of the region of the timefront in which strongly chaotic rays appear, and the strength of the rays’ sensitivity to initial conditions, are found to depend on the average (range-independent) sound-speed profile, on the range from the source to the receiver, and on the internal-wave spectral model, but not on the specific realization of the internal waves. For a particular experiment (SLICE89), it is concluded that the observed depth diffusion of energy in the late-arriving portion of the timefront is a result of refraction (of geometrical-optics rays), not diffraction. It is found that internal-wave effects cause an upper turning point of a ray to be spread to the extent of 10 km horizontally and 100 m vertically, which affects the resolution of ocean-acoustic tom.
A note on inverse probability

The problem of statistical investigation is the description of a population, or Kollektiv, of which a sample has been observed. At best we can only state the probability that certain parameters of this population lie within assigned limits, i.e. specify their probability density. It has been shown, e.g. by von Mises(1), that this is only possible if we know the probability distribution of the parameter before the sample is taken. Bayes' theorem is based on the assumption that all values of the parameter in the neighbourhood of that observed are equally probable a priori. It is the purpose of this paper to examine what more reasonable assumption may be made, and how it will affect the estimate based on the observed sample.
Closed-form solution of pure proportional navigation

The closed-form solution of the equations of motion of an ideal missile pursuing a nonmaneuvering target according to the pure proportional navigation law is obtained as a function of the polar coordinates for all real navigation constants N>or=2. The solution is given in the form of a uniformly convergent infinite product which reduces to a product of a finite number of factors if the navigation constant is a rational number. The solution is discussed, and necessary and sufficient conditions are stated for vanishing, bounded, and unbounded missile acceleration in the final phase of pursuit. >
Significance Tests and Goodness of Fit in the Analysis of Covariance Structures

Factor analysis, path analysis, structural equation modeling, and related multivariate statistical methods are based on maximum likelihood or generalized least squares estimation developed for covariance structure models. Large-sample theory provides a chi-square goodness-of-fit test for comparing a model against a general alternative model based on correlated variables. This model comparison is insufficient for model evaluation: In large samples virtually any model tends to be rejected as inadequate, and in small samples various competing models, if evaluated, might be equally acceptable. A general null model based on modified independence among variables is proposed to provide an additional reference point for the statistical and scientific evaluation of covariance structure models. Use of the null model in the context of a procedure that sequentially evaluates the statistical necessity of various sets of parameters places statistical methods in covariance structure analysis into a more complete framework. The concepts of ideal models and pseudo chi-square tests are introduced, and their roles in hypothesis testing are developed. The importance of supplementing statistical evaluation with incremental fit indices associated with the comparison of hierarchical models is also emphasized. Normed and nonnormed fit indices are developed and illustrated.
K-metric and K-normed linear spaces: survey.

We give a short survey on some fixed point theorems which are generalizations of the classical Banach-Caccioppoli principle of contractive mappings. All these results are gathered in three theorems about existence and uniqueness of fixed points for operators which act in $K$-metric or $K$-normed linear spaces and, in particular, in local convex spaces and scales of Banach spaces. Three fixed point theorems presented in this article cover numerous applications in numerical methods, theory of integral equations, some results on iterative methods for construction of periodic solution to ordinary differential equations, existence and uniqueness results on solvability for Cauchy and Goursat problems of Ovsjannikov - Treves - Nirenberg type and so on.
A Statistical Closure of a Low-Order Barotropic Model

In this paper, an attempt to close a low-order barotropic model for the neglected interactions in a perfect model setting is described. A barotropic T21 model with forcing and dissipation included is reformulated in terms of its EOFs. The EOFs are calculated from a long integration, and evolution equations are derived for the EOF amplitudes. A low-order EOF model is obtained by retaining only the 20 most dominant EOF structures and neglecting interactions with the remaining 211 EOFs. An attempt is made to describe the tendency error of the EOF model with a linear combination of resolved EOF amplitudes plus their quadratic combinations. The linear combination minimizes in a least squares sense the tendency error of the EOF model on the attractor of the full T21 model. It is found that, only if quadratic combinations of EOF amplitudes are taken into account, the closure reduces the tendency error substantially. The impact of the closure on the forecast skill of the EOF model is studied by making 100 3-week forecasts starting from independent initial conditions on the attractor of T21. The average useful forecast range increases from 12 days without closure to 18 days with closure. However, the method seems questionable in two aspects. First, the corrections to the coefficients of the evolution equations of the EOF amplitudes are as large as the coefficients themselves. Second, the closed EOF model could not simulate the climate. The closed model does not conserve energy in the absence of forcing and dissipation, and for this reason does not possess a stable attractor. Modifications to the proposed closure are mentioned to solve this problem. In conclusion, the proposed closure without the mentioned modifications leads to a statistical model that has an improved predictive skill but fails to simulate the climate of the original T21 barotropic model.
Electron thermal transport in RTP: filaments, barriers and bifurcations

Experiments with strong localized electron cyclotron heating (ECH) in the RTP tokamak show that electron heat transport is governed by alternating layers of good and bad thermal conduction. For central deposition hot filaments are observed inside the q = 1 radius. Moving the ECH resonance from the centre to the edge of the plasma results in discrete steps of the central electron temperature. The transitions occur when the minimum q value crosses q = 1,2,5/2 or 3, and correspond to the loss of a transport barrier situated close to the rational q value. Close to the transitions a new type of sawtooth activity is observed, characterized by the formation of sharp off-axis maxima on the profile, which collapse abruptly. The formation of the off-axis maxima is attributed to heat deposition precisely `on top of' a transport barrier.
On the Curvature of an Euler–Bernoulli Beam

This paper deals with different approaches to describing the relationship between the bending moment and curvature of a Euler—Bernoulli beam undergoing a large deformation, from a tutorial point of view. First, the concepts of the mathematical and physical curvature are presented in detail. Then, in the case of a cantilevered beam subjected to a single moment at its free end, the difference between the linear theory and the nonlinear theory based on both the mathematical curvature and the physical curvature is shown. It is emphasized that a careless use of the nonlinear mathematical curvature and moment relationship given in most standard textbooks may lead to erroneous results. Furthermore, a numerical example is given for the reader to make a quantitative assessment.
Frequency sweeping tests for asymptotic stability: a model transformation for multiple delays

Focuses on stability properties of linear delay-differential systems involving multiple discrete delays. Sufficient conditions for characterizing bounded and unbounded stability regions in the delays-parameter space are derived. The proposed results are expressed in terms of structured singular values and consist of some frequency sweeping tests, which improve (or recover) previous delay-dependent (delay-independent or mixed) criteria from the literature. Comments on the conservatism of the method are also considered.
Full-wave analysis of three-dimensional planar structures

An efficient numerical-analytical approach to the analysis of planar and waveguide three-dimensional structures is presented. To maintain high accuracy and fast convergence of solutions, the technique has been based on Galerkin's method in the spectral domain. The following has been achieved: (1) formulation of a diagonalized set of integral equations for problems associated with planar structures on multilayered uniaxial dielectric substrates; (2) development and application of complete orthonormalized sets of basis functions accounting the edge conditions in explicit form; and (3) development of efficient numerical quadratures for evaluating infinite singular integrals and improvement of the convergence of the integrals and series in the matrix elements of the algebraic system. >
ISOCAM-CVF imaging of M 16

We present ISOCAM observations (5-17m) of the HST M 16 field, including the striking elephant trunk struc- tures. The spectroscopic data have been obtained using the ISOCAM-CVF low-resolution mode, having a spectral resolution of40 (=) and a pixel size of 6 00 . The spectra show a combination of Unidentified Infrared Band (UIB) emission centred at 6.2, 7.7, 8.6, 11.3 and 16.4m, and atomic fine-structure lines of (ArII) 7.0 m, (ArIII) 9.0m, (SIV) 10.5m, (NeII) 12.8m and (NeIII) 15.6m. The spectra were decomposed by fitting a combination of Lorentzian line profiles and a blackbody curve to the data to produce maps of the spatial distribution of the fine-structure and UIB emission features. These maps have been compared with VLA radio, 450m SCUBA maps, 12 CO (J= 1 0) maps, and broadband filters ISOCAM LW2 (5-8.5m) and LW3 (12-18m) observations. Decomposed spectral features have shown that the LW2 filter is dominated by UIB emission and the emission observed in the LW3 filter is a combination of Neon fine-structure lines and a steep continuum, with the continuum dominating. Using the photoionisation code CLOUDY we have produced theoretical values for the fine-structure ratio of (NeIII) 15.6m/(NeII) 12.8m, from which we have calculated the eective ionising flux impinging onto the tips of the pillars to be1 3 10 10 photons cm 2 s 1 , consistent with estimates made from VLA observations.
Statistical hydromechanics of disperse systems. Part 3. Pseudo-turbulent structure of homogeneous suspensions

The theory of concentrated two-phase mixtures developed in the previous parts of this paper is applied to analysis of the structure of the local random motion (pseudo-turbulence) occurring in flows of suspensions of small solid spheres. Suspensions under study are assumed to be locally homogeneous in the sense that large-scale agglomerates of many particles or voids filled with the pure liquid do not arise in their flows and particles can be approximately regarded as statistically independent units. Coefficients of the particle diffusion caused by pseudo-turbulence are calculated without restrictions imposed on the value of the Reynolds number Re characterizing the fluid flow around one particle. Other pseudo-turbulent quantities (the r.m.s. pseudo-turbulent velocities of both phases, their effective pseudo-turbulent viscosities in a shear flow, etc.) are considered for small Re. In particular, a natural explanation is given to the known effect of the reduced hydraulic resistance of a fluidized bed as compared with that of a stationary particulate bed of the same porosity. Additionally, some properties of the mean motion of a suspension influenced by pseudo-turbulence are discussed brifly. By way of example, two problems are considered: stability of the upward flow of a homogeneous suspension with respect to small perturbations depending upon the vertical co-ordinate and time, and the spatial distribution of particles suspended by the upward flow of a fluid under gravity.
MODELING THERMAL IMPACT OF WILDLAND FIRES ON STRUCTURES IN THE URBAN INTERFACE. PART 1: RADIATIVE AND CONVECTIVE COMPONENTS OF FLAMES REPRESENTATIVE OF VEGETATION FIRES

ABSTRACT A 3-D computational fluid dynamics model is used to estimate the thermal impact on structures exposed to fire in the urban interface. The burning of vegetation is represented by a well-adjusted gas burner diffusion flame. This article examines two situations, depending on which modes of heat transfer from the flame are considered. Model predictions reveal how the presence of the structure modifies the dynamic flow pattern, which in turn may cause the overattachment of the fire plume to the structure and then the enhancement of thermal impact. Numerical results, including flame geometry, are found to be consistent with experimental observations.
Convection in a saturated porous medium at large Rayleigh number or Peclet number

When the dimensions of a convective system in a saturated porous medium are sufficiently great, diffusion effects can be neglected except in regions where the gradients of fluid properties are very large. A boundary-layer theory is developed for vertical plane flows in such regions. In special cases, the theory is equivalent to that for laminar incompressible flow in a two-dimensional half-jet, or in a plane jet or round jet, for which similarity solutions are well known. A number of experiments have been performed using a Hele-Shaw cell immersed in water, with a source of potassium permanganate solution located between the plates. At very small values of the source strength, a flow analogous to that of a plane jet from a slit is obtained. The distance advanced by the jet front, or cap, is measured as a function of time, and the velocity is found to be nearly proportional to the velocity of the fluid on the axis of the steady jet behind the cap, as given by the similarity law of Schlichting and Bickley. At large values of the source strength, a two-dimensional ‘broad jet’ of homogeneous solution descending under gravity is produced; the shape of the flow region can be calculated with little error from potential theory, neglecting the effect of the mixing layers. A possible example of a mixing layer observed in a geothermal region is examined. The theoretical form of the temperature distribution is calculated numerically, taking into account the large viscosity variation with temperature and also the possibility of a large permeability variation. These effects are found to have less influence upon the solution than might have been expected. Quantitative values obtained for the physical parameters are consistent with other geophysical observations.
Asymptotic speed of spreading of a nonlocal delayed equation without quasimonotonicity

This paper is concerned with the asymptotic speed of spreading of a nonlocal delayed equation, which does not satisfy the local quasimonotonicity. By constructing auxiliary undelayed equations, the asymptotic speed of spreading is established. In particular, for such a nonmonotonic equation, the asymptotic speed of spreading is the same as that in the corresponding undelayed equation.
THE LOCATION OF SOLAR METRIC TYPE II RADIO BURSTS WITH RESPECT TO THE ASSOCIATED CORONAL MASS EJECTIONS

Forty-one solar type II radio bursts located close to the solar limb (projected radial distance r ≳ 0.8 R☉) were observed at 109 MHz by the radioheliograph at the Gauribidanur observatory near Bangalore during the period 1997–2007. The positions of the bursts were compared with the estimated location of the leading edge (LE) of the associated coronal mass ejections (CMEs) close to the Sun. 38/41 of the type II bursts studied were located either at or above the LE of the associated CME. In the remaining 3/41 cases, the burst was located behind the LE of the associated CME at a distance of <0.5 R☉. Our results suggest that nearly all the metric type II bursts are driven by the CMEs.
Power adaptation for a mobile agent network

We study the problem of synchronizing a moving agent network by means of power adaptation strategy in the case where each agent is assigned power to establish directed connections with those of neighboring agents, and the power of each agent develops adaptively according to the local property between the agent and its neighbors. We show that our strategy is effective in achieving synchronization of the mobile agent network when selecting a proper operating parameter. In particular, we investigate the effect of the operating parameter on network synchronization by evaluating convergence time and energy efficiency.
Integral quadratic constraints for monotonic and slope restricted diagonal operators

Studies the description, by means of integral quadratic constraints (IQCs), of a class of static diagonal operators with equal diagonal entries. In particular, the diagonal entries considered are monotonic and slope-restricted nonlinearities. First, we give new IQCs for this type of operators which exploit the equality among nonlinearities. Then we show how these results can be used to derive new stability conditions for systems containing repeated nonlinearities. A simple example shows that the new description can substantially reduce conservativeness, with respect to previous existing techniques, in the analysis of systems with diagonal operators.
Dispersion relation and wave solution for anharmonic lattices and Korteweg De Vries continua

The set of coupled difference equations describing the dynamics of a monatomic chain is reduced to that of uncoupled anharmonic oscillators through the use of the translational invariance of the equations. Poincaré’s perturbation scheme is then used to obtain a space- and time-wise periodic wave solution together with a nonlinear dispersion relation between frequency, wavenumber and the amplitude. For all wavelengths, the frequency of vibration is observed to increase beyond the corresponding value for the linear case by terms proportional to the square of the amplitude multiplied by the coefficients of the cubic as well as quartic interactions. This solution of the lattice equations suggests a class of solutions of the generalized Korteweg-de Vries (K. de V.) equation which is related to the long wave limit of the nonlinear lattice by means of a semicharacteristic variable stretching transformation. Numerical results for the dispersion relations are presented for the semi-empirical Morse, Born-Meyer and Lennard-Jones potentials. For these physical examples, the contributions of the cubic and quartic terms of the interaction potential are found to be of the same order.
On the Algebraic Relationships of Trees, Co-Trees, Circuits, and Cutsets of a Graph

Algebraic relationships between trees, ( k trees) and circuits, co-trees (co- k trees) and cutsets of a graph are presented. They may be considered as a generalization and an extension of Hakimi and Green's technique of enumerating trees and k trees. Algebraic relationships for generating trees and co-trees by elementary transformations are also given.