Miracle-dz/UniFAR-FTUs huggingface dataset:
Momentum Transport by Gravity Waves

Abstract The momentum flux by orographic gravity waves and the turbulent heat flux in wave-breaking regions are estimated from aircraft data from ALPEX. The fluxes on 6 March 1982 are controlled by low-level directional shear of the mean flow and associated critical level with wave stress decreasing toward the critical level. On 25 March 1982 a critical level does not occur and wave stress is approximately constant with height within the observational domain. The calculation of these fluxes appears to be the first direct comparison between simple models of gravity-wave momentum flux and observed atmospheric fluxes. To develop a simple formulation of gravity wave drag for large-scale models, the gravity-wave stress super-saturation theory by Lindzen is generalized for the application to vertically varying mean flows. The wave momentum flux estimated from the generalized model agrees well with the observations for the two ALPEX days. For the 6 March case, the vertical divergence of wave momentum flux below .
High resolution coherence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography

In this paper we demonstrate a novel application of correlation mapping optical coherence tomography (cm-OCT) for volumetric nailfold capillaroscopy (NFC). NFC is a widely used non-invasive diagnostic method to analyze capillary morphology and microvascular abnormalities of nailfold area for a range of disease conditions. However, the conventional NFC is incapable of providing volumetric imaging, when volumetric quantitative microangiopathic parameters such as plexus morphology, capillary density, and morphologic anomalies of the end row loops most critical. cm-OCT is a recently developed well established coherence domain magnitude based angiographic modality, which takes advantage of the time-varying speckle effect, which is normally dominant in the vicinity of vascular regions compared to static tissue region. It utilizes the correlation coefficient as a direct measurement of decorrelation between two adjacent B-frames to enhance the visibility of depth-resolved microcirculation.
Regularized Bayesian estimation of generalized threshold regression models.

Estimation of threshold parameters in (generalized) threshold regression models is typically performed by maximizing the corresponding pro file likelihood function. Also, certain Bayesian techniques based on non-informative priors are developed and widely used. This article draws attention to settings (not rare in practice) in which these standard estimators either perform poorly or even fail. In particular, if estimation of the regression coeffcients is associated with high uncertainty, the pro file likelihood for the threshold parameters and thus the corresponding estimator can be highly aff ected. We suggest an alternative estimation method employing the empirical Bayes paradigm, which allows to circumvent defi ciencies of standard estimators. The new estimator is completely data-driven and induces little additional numerical e ffort compared with the old one. Simulation results show that our estimator outperforms commonly used estimators and produces excellent results even if the latter show poor performance. The practical relevance of our approach is illustrated by a real-data example; we follow up the anlysis of cross-country growth behavior detailed in Hansen (2000).
An efficient and simple refined theory for buckling and free vibration of exponentially graded sandwich plates under various boundary conditions

In this paper, an efficient and simple refined shear deformation theory is presented for the vibration and buckling of exponentially graded material sandwich plate resting on elastic foundations under various boundary conditions. The displacement field of the present theory is chosen based on nonlinear variations in the in-plane displacements through the thickness of the plate. By dividing the transverse displacement into the bending and shear parts and making further assumptions, the number of unknowns and equations of motion of the present theory is reduced and hence makes them simple to use. Equations of motion are derived from Hamilton’s principle. Numerical results for the natural frequencies and critical buckling loads of several types of symmetric exponentially graded material sandwich plates are presented. The accuracy of the present theory is verified by comparing the obtained results with solutions available in the literature. Numerical results show that the present theory can archive accuracy comparable to the existing higher order shear deformation theories that contain more number of unknowns.
Optimal Control of Nanosatellite Fast Deorbit Using Electrodynamic Tether

This paper proposes a piecewise two-phased optimal control scheme for fast nanosatellite deorbit by a short electrodynamic tether. The first phase concerns the open-loop control trajectory optimization, where the optimal control problem is formulated only for the tether libration motion by assuming the slow-varying orbital elements of the electrodynamic tether system as constant within a discretized interval. The second phase deals with the closed-loop optimal control for tracking the derived optimal reference trajectory subject to multiple major orbital perturbations. The finite receding horizon control method is used in the optimal trajectory tracking. Both optimal control problems are solved by a direct collocation method based on the Hermite–Simpson method using discretization schemes with coincident nodes. The resulting nonlinear programming problem significantly reduces the problem size and improves the computational efficiency. Numerical results for fast nanosatellite deorbit by an electrodynamic t.
Dielectric and piezoelectric activities in (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals from 5 K to 300 K

Lead based relaxor single crystals have raised a considerable interest due to their outstanding piezoelectric properties. These piezoelectric properties are temperature dependent and are known to decrease when the temperature is decreased. The aim of this paper is to study the variation of the dielectric constant, the elastic compliance, the coupling factor, the piezoelectric charge coefficient, and the mechanical quality factor for rhombohedral single crystals of (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMN-PT) poled along [001] in the 5 K–300 K temperature range. In particular, it has been shown that a relaxation phenomenon occurs around 100 K leading to a rapid decrease of the studied piezoelectric, mechanical, and dielectric constants just after a plateau. As a consequence, the similar behaviour of the dielectric constant, piezoelectric charge coefficient, and elastic compliance versus temperature leads to a temperature independent behaviour of the coupling factor above 100 K. This relaxation is also responsibl.
FINITE VOLUME METHOD FOR PREDICTION OF FLUID FLOW IN ARBITRARILY SHAPED DOMAINS WITH MOVING BOUNDARIES

In this paper a method is presented that can be used for both the Lagrangian and the Eulerian solution of the Navier–Stokes equations in a domain of arbitrary shape, bounded by boundaries which move in any prescribed time-varying fashion. The method uses the integral form of the governing equations for an arbitrary moving control volume, with pressure and Cartesian velocity components as dependent variables. Care is taken to also satisfy the space conservation law, which ensures a fully conservative computational procedure. Fully implicit temporal differencing makes the method stable for any time step. A detailed description is provided for the discretization in two dimensions, with a collocated arrangement of variables. Central differences are used to evaluate both the convection and diffusion fluxes. The well known SIMPLE algorithm is employed for pressure–velocity coupling. The resulting algebraic equation systems are solved iteratively in a sequential manner. Results are presented for a flow in a channel with a moving indentation; they show favourable agreement with experimental observations.
Shorted spiral-like printed antennas

We present two electrically small printed antennas suitable for mobile communication handset terminals. The conductor shapes of the proposed shorted patch antennas maximize the length of the current path for a given area thereby significantly reducing the resonant frequency of the antenna. Reductions in operating frequencies of the order of seven to ten have been achieved.
Regional blow-up for a higher-order semilinear parabolic equation

We study the blow-up behaviour of solutions of a 2mth order semilinear parabolic equation [formula here] with a superlinear function q(u) for |u| Gt; 1. We prove some estimates on the asymptotic blow-up behaviour. Such estimates apply to general integral evolution equations. We answer the following question: find a continuous function q(u) with a superlinear growth as u → ∞ such that the parabolic equation exhibits regional blow-up in a domain of finite non-zero measure. We show that such a regional blow-up can occur for q(u) = u|ln|u‖2m. We present a formal asymptotic theory explaining that the stable (generic) blow-up behaviour as t → T− is described by the self-similar solution [formula here] of the complex Hamilton–Jacobi equation [formula here].
High peak power and high average power subnanosecond modulator operating at a repetition frequency of 3.5 kHz

This paper presents results of tests of a hybrid subnanosecond modulator with an output resistance of 45 /spl Omega/. The modulator comprises an all-solid-state nanosecond charger, which is equipped with an inductive energy store and a semiconductor opening switch, and a pulse peaker with hydrogen spark gaps. The modulator generates stable pulses-(180 to 200) kV in amplitude and 400 to 700 ps long at a pulse repetition rate of up to 3.5 kHz. An average output power of 1.5 kW was achieved under the pulse burst mode.
Asymptotic distributions of weighted pontograms under contiguous alternatives

Let {N(x), x ≥ 0} be a non-homogeneous, also called non-stationary, Poisson process with density function λ(x), x ≥ 0. We consider the problem of testing the null hypothesis of λ(x) having a constant value against the alternative that λ(x) is a function of x.
The satellite population of the Milky Way in a ΛCDM universe

We compare the structure and kinematics of the 11 known satellites of the Milky Way with high-resolution simulations of the formation of its dark halo in a ACDM universe. In contrast to earlier work, we find excellent agreement. The observed kinematics are exactly those predicted for stellar populations with the observed spatial structure orbiting within the most massive 'satellite' substructures in our simulations. Less massive substructures have weaker potential wells than those hosting the observed satellites. If there is a halo substructure 'problem', it consists of understanding why halo substructures have been so inefficient in making stars. Suggested modifications of dark matter properties (for example, self-interacting or warm dark matter) may well spoil the good agreement found for standard cold dark matter.
Density currents or density wedges: boundary-layer influence and control methods

Density currents and density wedges are two observed manifestations of interactions between an ambient flow and a horizontal buoyant intrusion. In a density current the buoyant pressure force is primarily balanced by the local form drag of the current head which has a blunt shape and abrupt depth change. In a density wedge a distributed interfacial drag is the primary balancing force, leading to a stretched-out shape and long-distance intrusions. A perturbation analysis of the approach flow to the inclined front of a density current shows that slight momentum changes caused by viscous effects in the ambient flow determine which of these two flow types is established. In a uniform ambient channel flow, any momentum deficit relative to the inviscid case will lead to a local flattening of the front and ultimate breakdown into a density wedge. On the other hand, a momentum surplus will support a steady-state density current. Several exploratory experiments on control of the ambient boundary layer through local non-uniformities were performed with the objective of achieving stable density-current forms with limited intrusion lengths. These methods include a small step, a barrier and suction and are applied for intrusions at either the bottom or surface of an ambient water flow. In all cases, good agreement is found with the force balances predicted by Benjamin's (1968) theory and its extension by Britter & Simpson (1978) which accounts for entrainment in the wake zone of the head.
Thermal dispersion from a line source in the shearless turbulence mixing layer

We experimentally investigate dispersion from a heated line source placed in the central region of a turbulence mixing layer. Recently described by Veeravalli & Warhaft (1989) the mixing layer has no mean shear and consists of gradients in the velocity variance and scale; it is formed from a composite grid of constant solidity from which two distinct velocity scales are formed, one on either side of the stream. Mixing is effected by intermittent turbulent penetration and diffusion. The dispersion measurements were carried out in the convective regime where both plume flapping and fine-scale turbulent mixing play a role, the latter becoming more dominant as the plume evolves. The mean and variance temperature profiles are strongly skewed (with larger tails on the low turbulence side of the flow) in the earlier stages of the plume development. Here, in the convective range, the median and peak of the mean plume are deflected toward the large-scale region. As the flow evolves the profiles become more symmetrical but as the plume enters the turbulent diffusive stage there is evidence that the profiles again became asymmetric but now with longer tails in the high turbulence side of the flow (owing to the higher diffusivity). The temperature variance and heat flux budgets are highly asymmetric but tend to exhibit many of the characteristics of the budget of a line source in decaying homogeneous grid turbulence which is also presented here. However, a distinct region of negative production (counter-gradient heat flux) is found in the temperature variance budget and this is shown to be a consequence of the asymmetry of the transverse velocity probability density function in the mixing layer. Temperature spectra, both of the time series and of the intermittency function, across the plume are described. They are shown to peak at high wavenumbers in the centre and edge of the plume and at lower wavenumbers in the intermediate region. Their form is shown to change as the plume develops fine-scale structure and flapping becomes less important.
Numerical Modeling of Free Overfall

Free overfall is treated by using two-dimensional steady potential flow theory. Based on the theory of the boundary value problem of analytical function and the substitution of variables we derive the boundary integral equations in the physical plane for solving the free overfall in a rectangular channel. A numerical iterative method has been developed to solve these boundary integral equations. The free water surface profiles, pressure distribution, and the end-depth ratio are calculated for a wide range of bed slopes, bed roughness, and incoming upstream Froude number. The computed results agree well with the available experimental data.
The way adults with orientation to mathematics teaching cope with the solution of everyday real-world problems

The article aims to check the way adults, some who are practicing mathematics teachers at elementary school, some who are academicians making a career change to mathematics teachers at junior high school and the rest who are pre-service mathematics teachers at elementary school, cope with the solution of everyday real-world problems of buying and selling. The findings show that even adults with mathematical background tend to make mistakes in solving everyday real-world problems. Only about 70% of the adults who have an orientation to mathematics solved the sample problem correctly. The lowest percentage of success was demonstrated by the academicians making a career change to junior high school mathematics teachers whereas the highest percentage of success was manifested by pre-service elementary school mathematics teachers. Moreover, the findings illustrate that life experience of the practicing mathematics teachers and, mainly, of the academicians making a career change, who were older than the pre-service teachers, did not facilitate the solution of such a real-world problem. Perhaps the reason resides in the process of mathematics teaching at school, which does not put an emphasis on the solution of everyday real-world problems.
High‐resolution radar observations of daytime kilometer‐scale wave structure in the equatorial electrojet

Using a new antenna configuration and new data processing hardware, the authors probed the electrojet with unprecedented spatial resolution in January 1991 at Jicamarca. The altitude resolution was 125 m, and the east-west antenna beamwidth was about 0.6[degrees], or about 1 km at electrojet altitudes. The high spatial resolution allowed them to observe, at certain altitudes and times, pronounced wavelike structures with vertical wavelengths of the order of 1 km and periods of tens of seconds. These observations closely resemble the predictions of recent nonlocal, nonlinear numerical simulations of large-scale turbulence in the equatorial electrojet. The comparison demonstrated the validity of the theory and confirmed the idea that the Doppler power spectra of type 2 echoes at 50 MHz (due to 3-m plasma waves generated by the gradient-drift instability and a nonlinear cascade of energy from long-wavelength modes to short) are controlled primarily by the large-scale dynamics and not by the nonlinear local growth and decay rates of the 3-m waves themselves. 16 refs., 7 figs.
Simple force expressions for idealized saturable poles and wedges

Force expressions are presented for simple idealized magnetic pole geometries with (a) infinitely permeable pole material, (b) "square B/H" saturable pole material, and (c) "square M/H" saturable material, the third being the most realistic. The simplicity of the force expressions with saturation is surprising, and important conclusions can be drawn about the role of saturation, the effects of different iron saturation models, and details of the field. For example, for the fundamentally important saturable overlapping rectangular pole configuration, with saturable poles modeled as highly nonlinear, "square M/H" iron, the useful transverse force for positive overlaps is F=/spl mu//sub 0/M/sub s/F, twice a comparable value for infinitely permeable poles. This paper is an exploration of how far one can go, using a variety of analytical nonnumerical techniques, in determining fields and forces when saturation effects predominate. The results give useful insights not easily obtained from numerical solutions and provide exact results in certain cases.
Infrared spectroscopy of Nova Cassiopeiae 1993 — II. Evolution of the dust

We present infrared spectroscopy of the nova V705 Cas (1993), obtained following the dust formation episode. There is 'UIR' emission at 3.3, 3.4, 8.2, 8.7 and 11.4 mu m, and silicate emission at 9.7 mu m. The UIR features are unlike those seen in most other objects displaying UIR emission, but are broadly similar to those present in the infrared spectra of the nova V842 Cen and some post-AGE stars. The 3.4/3.3 flux ratio is large compared with that usually seen in the spectra of objects displaying the UIR features, and the '7.7' feature appears at 8.2 mu m. We determine the beta-index for nova dust for the first time; the beta-index changed over the period 1994 August 22 (day 251; beta similar or equal to 0.8) to 1994 October/November (day 300/341; beta = 0.3), suggesting that grain growth continued to occur. The grains attained dimensions greater than or similar to 0.5 mu m. We estimate that about 10(-8) M. of carbon dust condensed in the ejecta. The profile of the 9.7-mu m silicate emission feature was somewhat narrower than in other novae displaying this feature, suggesting that the silicate in V705 Cas may have been amorphous.
Double‐wall nanotube as vibrational system: Mathematical approach

In this paper, we present a recently developed mathematical model for short double‐wall carbon nanotubes. The model is governed by a system of four hyperbolic equations representing the two Timoshenko beams coupled through the Van der Waals forces. The system is equipped with a four‐parameter family of the boundary conditions and can be reduced to an evolution equation. This equation defines a strongly continuous semi‐group. Spectral properties of the semi‐group generator are presented in the paper. We show that it is an unbounded non‐selfadjoint operator with compact resolvent. Moreover, this operator is a relatively compact perturbation of a certain selfadjoint operator. Copyright © 2008 John Wiley & Sons, Ltd.
Linear regression in astronomy. II

Five methods for obtaining linear regression fits to bivariate data with unknown or insignificant measurement errors are discussed: ordinary least-squares (OLS) regression of Y on X, OLS regression of X on Y, the bisector of the two OLS lines, orthogonal regression, and 'reduced major-axis' regression. These methods have been used by various researchers in observational astronomy, most importantly in cosmic distance scale applications. Formulas for calculating the slope and intercept coefficients and their uncertainties are given for all the methods, including a new general form of the OLS variance estimates. The accuracy of the formulas was confirmed using numerical simulations. The applicability of the procedures is discussed with respect to their mathematical properties, the nature of the astronomical data under consideration, and the scientific purpose of the regression. It is found that, for problems needing symmetrical treatment of the variables, the OLS bisector performs significantly better than orthogonal or reduced major-axis regression.
Dominance analysis: A new approach to the problem of relative importance of predictors in multiple regression.

Whenever multiple regression is used to test and compare theoretically motivated models, it is of interest to determine the relative importance of the predictors. Specifically, researchers seek to rank order and scale variables in terms of their importance and to express global statistics of the model as a function of these measures. This article reviews the many meanings of importance of predictors in multiple regression, highlights their weaknesses, and proposes a new method for comparing variables: dominance analysis. Dominance is a qualitative relation defined in a pairwise fashion: One variable is said to dominate another if it is more useful than its competitor in all subset regressions. Properties of the newly proposed method are described and illustrated
A geometrical approach for the identification of state space models with singular value decomposition

Some geometrically inspired concepts are studied for the identification of models for multivariable linear time-invariant systems from noisy input-output observations. Starting from a fundamental highly structured input-output matrix equation, it is shown how the singular value decomposition allows the order of the observable part of the system and its state-space model matrices to be estimated. Moreover, conditions for persistency of excitation of the inputs and the behavior of the algorithm when the data are perturbed by noise can easily be studied from a geometrical point of view. The singular values allow these concepts to be quantified. An example with an industrial plant identification is presented. <<ETX>>