Miracle-dz/UniFAR-FTUs huggingface dataset:
Do orographic gravity waves break in flows with uniform wind direction turning with height?

The properties and behaviour of orographically generated gravity waves which have a vertical component of propagation are examined by analysing the structure of stationary, hydrostatic waves embedded in a basic state wind field, U, whose direction and magnitude may vary linearly with height, z. From a ray‐tracing analysis it is evident that the wave energy density decays to zero approaching a three‐dimensional (3‐D) critical level in such an ambient flow field where U. k = 0 for the particular horizontal wave vector k = (k, l, 0). This decay of the wave energy density would appear to imply that wave breaking does not naturally occur in 3‐D flows where the wind turns uniformly with height (excepting that wave vectors which do not experience a 3‐D critical level can break due to the decrease of density with height). However, as a linear theory analysis of convective overturning demonstrates, the criterion for wave breaking relaxes as a 3‐D critical level is approached. the gravity wave amplitude is only required to exceed the inverse of the vertical wave number (which is proportional to U. k and decays to zero at the critical level) for overturning to occur. Consequently a linear estimate of whether convective instability will occur depends on the asymptotic limit of the ratio of the wave energy density to the square of the amplitude. It can be shown from the ray‐tracing analysis that for 3‐D flow fields with a mean wind which turns uniformly with height this ratio diverges, implying that the criterion for convective breaking of gravity waves will always be exceeded on approaching such a 3‐D critical level.
The fine-scale intermittency of turbulence

The technique of Rao et al. [J. Fluid Mech. 48, 339 (1971)], which consists of identifying pulses or regions of strong activity in a narrow bandpass filtered signal, is reexamined in the context of Sreenivasan’s theory [J. Fluid Mech. 151, 81 (1985)], by applying it to white noise and turbulent signals. For white noise, the dependence of pulse characteristics on the threshold and filter center frequency are in close agreement with the theory. There are, however, important differences between white noise and turbulence results, even when the white noise spectrum is shaped to simulate the turbulent spectrum. For the turbulent signal, the theory is valid only for a range of filter parameters for which the departure of the filtered signal from a Gaussian distribution is small. Using wall shear stress and velocity fluctuations in a fully developed turbulent duct flow, the pulse frequency is found to be closely related to the zero‐crossing frequency. It is concluded that the pulse frequency, which is proportion.
Inconsistency in Addition and Subtraction Strategies

AbstractSecond and third graders (N = 168) from six Dutch elementary schools participated in this study. They were asked to solve two sets of almost identical sums at a 2-week interval. Inconsistency was defined as using two different strategies to solve two almost identical sums. The subjects’ verbal reports indicated, first, that inconsistency in strategy use is a fairly widespread phenomenon: about half of the subjects were inconsistent. This inconsistency was not related to children’s arithmetical flexibility and ability nor to different instructional methods. Second, inconsistency was more frequent with relatively unfamiliar sums. Third, inconsistency in strategy use can result in irregularly appearing and hence misinterpreted errors.
Electromagnetic Characterization of Symmetric and Asymmetric Modes in a Disk-Loaded Structure

The electromagnetic (EM) characteristics of symmetric and asymmetric modes in a disk-loaded structure have been investigated. The study focused on those EM characteristics that affect the dynamics of electrons in amplifier. Two different frequency bands have been considered, X-band and Ka-band, referring to two main activities at Stanford Linear Accelerator Center and Cornell University. The impact of the geometry on the EM characteristics is presented and some simple analytic relations have been developed based on simulations.
Obscuration and the various kinds of Seyfert galaxies

For a complete hard X-ray selected sample of active spiral galaxies we have collected luminosities of HX = L/sub x/ (2--10 keV), H.beta. lambda4861, (O III) lambda5007, and 3.5 . mu.m (L3.5). The effect found by Keel, that optically selected Seyfert galaxies tend to be face-on, is removed. Most of the X-ray discovered objects are ''narrow emission line galaxies'' (NELGs). We find that they are both selectively edge-on and lower in HX than the sample as a whole. At least some NELGs have large X-ray absorbing columns, so we believe that both the axial ratio and luminosity effects are due to obscuration. We also find that edge-on galaxies have low H.beta. /HX; however, no effect with axial ratio is seen with O III/HX or L3.5/HX. We thus believe that obscuration takes place in or just around the broad line region (BLR), which has a flattened configuration parallel to the disk of the parent galaxy.
Towards a better understanding of dielectric barrier discharges in ferroelectrets: Paschen breakdown fields in micrometer sized voids

Charged cellular polypropylene foams (i.e., ferro- or piezoelectrets) demonstrate high piezoelectric activity upon being electrically charged. When an external electric field is applied, dielectric barrier discharges (DBDs) occur, resulting in a separation of charges which are subsequently deposited on dielectric surfaces of internal micrometer sized voids. This deposited space charge is responsible for the piezoelectric activity of the material. Previous studies have indicated charging fields larger than predicted by Townsend's model of Paschen breakdown applied to a multilayered electromechanical model; a discrepancy which prompted the present study. The actual breakdown fields for micrometer sized voids were determined by constructing single cell voids using polypropylene spacers with heights ranging from 8 to 75 μm, “sandwiched” between two polypropylene dielectric barriers and glass slides with semi-transparent electrodes. Subsequently, a bipolar triangular charging waveform with a peak voltage of 6 .
New Theoretical View for High Temperature Superconductivity

A new theoretical explanation is given for the superconducting state in copper oxides. The key feature of the state is the following. A coherent motion of itinerant holes from low-spin to high-spin states in the presence of a relatively long-range antiferromagnetic ordering of the Cu localized spins creates a superconducting state. Based on this state, it is suggested that the attractive interaction between two holes in different energy bands with the same dispersion mediated by Jahn-Teller-type optic phonons is primarily responsible for superconductivity.
Consistency of Hill's estimator for dependent data

Consider a sequence of possibly dependent random variables having the same marginal distribution F, whose tail 1−F is regularly varying at infinity with an unknown index − α < 0 which is to be estimated. For i.i. d. data or for dependent sequences with the same marginal satisfying mixing conditions, it is well known that Hill's estimator is consistent for α−1 and asymptotically normally distributed. The purpose of this paper is to emphasize the central role played by the tail empirical process for the problem of consistency. This approach allows us to easily prove Hill's estimator is consistent for infinite order moving averages of independent random variables. Our method also suffices to prove that, for the case of an AR model, the unknown index can be estimated using the residuals generated by the estimation of the autoregressive parameters.
The X-ray spectrum of AM Herculis from 0.1 to 150 keV

No significant flux at 100 keV was detected in the observations by the HEAO 1 satellite (March and April of 1978) and in several OSO 7 observations. The spectrum above 2 keV can be fitted by a composite thermal bremsstrahlung model that includes an approximation to the albedo expected from the white dwarf. The bremsstrahlung kT sub e from this model (30.9 + or - 4.5 keV) implies a white dwarf mass in excess of 0.6 solar mass. An emission feature at 6.5 + or - 0.15 keV and equivalent width of 0.8 + or - 0.1 keV is confirmed; it is thought that this might be due to fluorescence from the white dwarf by the bremsstrahlung from a small thin shocked region. It is noted that the continuum could also have been steepened at high energy in scattering in the accretion column, but the line photons cannot have gone through the same optical depths.
Blind CFO estimation based on decision directed MUSIC technique for interleaved uplink OFDMA

This paper deals with blind carrier frequency offset (CFO) estimation based on the multiple signal classification (MUSIC) criterion with Taylor series expansion for interleaved orthogonal frequency division multiple access uplink systems. An efficient estimator is suggested which finds a new CFO vector based on the Taylor series expansion of the one initially given in the presence of CFO. The problem of finding the new CFO vector is formulated as the closed form of a generalized eigenvalue problem, which allows one to readily solve it. Due to more accurate residual CFO estimate, which can provide more accurate residual CFO compensation, this paper also presents a decision-directed MUSIC scheme to improve the CFO estimation performance. The proposed estimator not only can estimate CFO, but also entail less computational load. Several computer simulation results are provided for illustrating the effectiveness of the proposed blind CFO estimator.
Observations of shock waves in cloud cavitation

This paper describes an investigation of the dynamics and acoustics of cloud cavitation, the structures which are often formed by the periodic breakup and collapse of a sheet or vortex cavity. This form of cavitation frequently causes severe noise and damage, though the precise mechanism responsible for the enhancement of these adverse effects is not fully understood. In this paper, we investigate the large impulsive surface pressures generated by this type of cavitation and correlate these with the images from high-speed motion pictures. This reveals that several types of propagating structures (shock waves) are formed in a collapsing cloud and dictate the dynamics and acoustics of collapse. One type of shock wave structure is associated with the coherent collapse of a well-defined and separate cloud when it is convected into a region of higher pressure. This type of global structure causes the largest impulsive pressures and radiated noise. But two other types of structure, termed ‘crescent-shaped regions’ and ‘leading-edge structures’ occur during the less-coherent collapse of clouds. These local events are smaller and therefore produce less radiated noise but the interior pressure pulse magnitudes are almost as large as those produced by the global events. The ubiquity and severity of these propagating shock wave structures provides a new perspective on the mechanisms reponsible for noise and damage in cavitating flows involving clouds of bubbles. It would appear that shock wave dynamics rather than the collapse dynamics of single bubbles determine the damage and noise in many cavitating flows.
Observations of the Crab pulsar and nebula by the EGRET telescope on the Compton Gamma-Ray Observatory

The Crab pulsar and nebula were observed three times in 1991 April to June by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO): April 23 to May 7, May 16 to 30, and June 8 to 15. The results of analysis of the gamma-ray emission in the energy range from 50 MeV to more than 10 GeV are reported. The observed gamma-ray light curve exhibits two peaks separated in phase by 0.40 +/- 0.02, consistent with previous observations. The total pulsed emission from the Crab pulsar is found to be well represented by a power-law spectrum, softer than the spectrum measured by COS B (Clear et al., 1987). The interpulse emission has a harder spectrum than either of the pulses. The evidence for pulsed emission above 5 GeV in the EGRET data is not conclusive. Unpulsed emission in the energy range 50 MeV to 5 GeV was detected, with an indication of a hardening of the unpulsed spectrum above about 1 GeV. There was a significant change in the light curve over the 2 months of these observations, although the shape of the spectrum remained constant.
Modular Representations of GL2 of a Local-Field: The Ordinary, Unramified Case

Abstract Let F be a local field of residue characteristic p , and let E be an algebraically closed field of characteristic p . We prove that unramified irreducible representations of PGL 2 ( F ) on E - vector spaces admit eigenvectors for an appropriate Hecke operator T . We classify them by the eigenvalue λ of T to one dimensional (λ = ± 1), principal series (λ ≠ 0, ± 1) or supersingular (λ = 0). Any λ can appear, and for λ ≠ 0 we prove uniqueness.
On Frame Wavelets Associated with Frame Multiresolution Analysis

Abstract We present some necessary and sufficient conditions for a frame multiresolution analysis (FMRA) to admit a frame wavelet whose dyadic dilations and integer translates generate a frame for L2( R ) and propose a construction of a wavelet, if it exists, which reduces to the classical orthonormal wavelet in the case of orthonormal multiresolution analysis. We also show that there always exists a frame for the detail space W0 of a frame MRA consisting of the integer translates of two functions and give an explicit construction of them.
Time-Space Discretization of the Nonlinear Hyperbolic System \protect\mbox\boldmath\lowercase$u_tt = \operatornamediv (\sigma(\mbox\boldmath\uppercase$D$u)+ \mbox\boldmath\uppercase$D$u_t)$

The numerical treatment of the hyperbolic system of nonlinear wave equations with linear viscosity, $u_{tt}= {\rm div}(\sigma(Du)+Du_t)$, is studied for a large class of globally Lipschitz continuous functions $\sigma$, including nonmonotone stress-strain relations. The analyzed method combines an implicit Euler scheme in time with Courant (continuous and piecewise affine) finite elements in space for a class of varying time steps with varying meshes. Explicit a priori error bounds in $L^\infty(L^2)$, $L^2(W^{1,2})$, and W1,2(L2) are established for the solutions of the fully discrete scheme.
Effect of preformed plasma on terahertz-wave emission from the plasma generated by two-color laser pulses

We introduced a weak prepulse 0-2 ns before the main pulse in the formation of a terahertz (THz) wave in air plasma by laser pulses composed of fundamental and second-harmonic waves. The prepulse suppressed the THz wave generated by the main pulse. We analyzed the suppression factor as a function of the time interval between the prepulse and the main pulse and found that the THz wave from the main pulse decreases immediately after the prepulse, recovers partially within several hundred picoseconds, and then recovers slowly. This suppression is attributed to the dense plasma, which absorbs and screens the generated THz wave, since the relaxation time is close to the lifetime of the fluorescence from the plasma. The results support the idea that the major mechanism of THz wave generation is explained by the plasma current model.
80 GHz field-effect transistors produced using high purity semiconducting single-walled carbon nanotubes

This paper presents the high frequency performance of single-walled carbon nanotube (SWNT) field-effect transistors, with channel consisting of dense networks of high purity semiconducting SWNTs. Using SWNT samples containing 99% pure semiconducting SWNTs, we achieved operating frequencies above 80 GHz. This record frequency does not require aligned SWNTs, thus demonstrating the remarkable potential of random networks of sorted SWNTs for high frequency electronics.
Temperature-dependent absorption derivative on InAs/GaSb Type II superlattices

We present an investigation of the quantum confined energy levels in a mid-wave infrared and long-wave infrared InAs/GaSb type II strained-layer superlattice (SLS) photodetector by computing the first derivative of the absorption spectra from 80K to 250K , with respect to the wavelength. Energy levels of both the fundamental transition and two other higher orders are identified for the SLS. The temperature evolution of each of these bands was also characterized by fitting the energy transitions to the Varshni equation, which showed that in general, the higher-energy transitions have a greater change in bandgap with temperature than the lower-energy ones. The transition energies appeared linearly dependent on the InAs layer thickness, and had a weaker dependence on the GaSb layer thickness. A feature that vanished at higher temperatures was also observed, which is due to a GaSb characteristic, rather than the superlattice.
Electron heated internal transport barriers in JET

By applying lower hybrid current drive (LHCD) for strong electron heating and off-axis current drive starting very early in the discharge, an electron internal transport barrier (eITB) can be generated. The barrier is formed just inside the location of minimum q, and slowly moves inward with this location. During the current flat-top the barrier can be sustained during many seconds, either with continued LHCD, or by ion cyclotron resonance heating. In this paper both scenarios are analysed and compared.
Shock‐wave initiation of heterogeneous reactive solids

Shock‐wave initiation of solid explosives depends on localized regions of high temperature (hot spots) created by heterogeneous deformation in the vicinity of various defects. Current mathematical models of shock initiation tend to fall into two broad categories: (1) thermodynamic‐state‐dependent reaction‐rate models, and (2) the continuum theory of multiphase mixtures. The level of generality possessed by (1) appears to be insufficient for representation of observed initiation phenomena, while that of (2) may exceed necessary requirements based on present measurement capabilities. As a means of bridging the gap between these two models, we present an internal‐state‐variable theory based on elementary physical principles, relying on specific limiting cases for the determination of functional forms. The appropriate minimum set of internal‐state variables are the mass fraction of hot spots μ, their degree of reaction f, and their average creation temperature θ. The overall reaction rate λ, then depends o.
Cosmic rays in star-forming galaxies

The energy density of cosmic ray protons (CRp) in star-forming environments can be (i) measured from γ-ray πo-decay emission, (ii) inferred from the measured radio non-thermal synchrotron emission (once a theoretical p/e ratio and particle-field equipartition have been assumed), and (iii) estimated from the observed supernova rate and the deduced CRp residency time. For most of the currently available galaxies where these methods can be simultaneously applied, the results of the various methods agree and suggest that CRp energy densities range from 𝒪(10−1) eV cm−3 in very quiet environments up to 𝒪(102) eV cm−3 in very active ones. The only case for which the methods do not agree is the Small Magellanic Cloud, where the discrepancy between measured and estimated CRp energy density may be due to a smaller characteristic CR confinement volume.
Respondent Jeopardy and Optimal Designs in Randomized Response Models

Abstract Randomized response methods allow different kinds and degrees of privacy depending upon models and parameters. A theoretical approach to efficiency is suggested based on minimizing variance for given privacy requirements. Privacy requirements are defined in units of jeopardy from different points of view and indexed by measures suggested by information theory. Variances of competing models are compared only when the procedures meet the privacy requirements in terms of not exceeding the maximal jeopardizing information allowable for the particular application. The approach is illustrated through developing minimum variance under given jeopardizing information restrictions for a general dichotomous-population-dichotomous-response model.
Collective, short-wavelength excitations in liquid gallium

Well-defined (i.e., not overdamped) collective excitations have been found in liquid Ga at 973 K (about 670 K above the melting point) by means of inelastic neutron scattering. The experimental results contrast with a previous investigation carried out at $T=326$ K (only 23 K above melting) where only heavily damped excitations were found, and partially agree with those of recently reported ab initio simulations for the high-temperature liquid. The interpretation of the experimental data is aided by results from a molecular dynamics simulation, which is carried out using an effective potential derived by inversion of the measured static structure factor. A comparison of experimental and simulation data reveals the mostly nonacoustic character of the excitations appearing at higher frequencies.
Size control of erbium-doped silicon nanocrystals

This work describes the effects of pyrolysis oven length and erbium precursor on the preparation of discrete erbium-doped silicon nanoparticles. These doped nanoparticles were prepared by the co-pyrolysis of disilane and the volatile complex Er(tmhd)3 (tmhd=2,2,6,6-tetramethyl-3,5-heptanedionato). The particle sizes and size distributions were determined using high resolution and conventional transmission electron microscopy. Erbium-doped silicon nanoparticles exhibit a selected area electron diffraction pattern consistent with the diamond cubic phase and a distinctive dark contrast in the transmission electron microscope. The presence of erbium is confirmed by x-ray energy dispersive spectroscopy. In general, the mean diameter of the individual nanoparticles increases as the length of the pyrolysis oven used during their preparation is increased.
Robust Cartesian Grid Flow Solver for High-Reynolds-Number Turbulent Flow Simulations

A novel, Cartesian-grid-based flow solver is developed for predicting complex high-Reynolds-number turbulent flowfields. The Cartesian grid generator is based on the cut-cell approach using cell merge and Cartesian layer techniques. Cartesian layers imitate the structured grid approach in which the mesh is stretched gradually. Local refinement is added based on local surface curvature. As a turbulence closure model, the two equation k–! -TNT turbulencemodel is successfully implemented using an unconditionally positive-convergent implicit time integration scheme. The overall flow solver’s robustness and accuracy are verified using three challenging test cases. The numerical results convincingly demonstrate the robustness and accuracy of the flow solver, especially in predicting aerodynamic forces.
A mathematical model of shading rows of plants

SYNOPSIS This paper reviews a previous analysis on the shading of buildings [1] and applies the same principles to applications in agriculture, e.g. the shading of rows of plants. The new model is applicable to vertical parallel rows of plants, such as the cordon-trained grapevine, aligned in any direction and on either horizontal or inclined slopes. At any particular plantation, information for optimal planting procedures could be determined. The plants could make a much greater use of solar energy compared with conventional procedures, with enhanced quality and quantity.