Miracle-dz/UniFAR-FTUs huggingface dataset:
Mitigating satellite motion in GPS monitoring of traveling ionospheric disturbances

We discuss the impact of satellite motion on the use of compact arrays of GPS receivers for estimating the velocity of traveling ionospheric disturbances (TIDs). It is shown that satellite motion has subtle effects upon standard techniques of waveform cross correlation, or time difference of arrival, which can easily lead to spurious TID velocity estimates. We present some improved techniques for cross‐correlating TID waveforms while taking account of the Doppler shifts created by satellite motion. In addition, we discuss some improved techniques for separating TID waveforms from background ionospheric trends, such as diurnal variation, based on high‐order polynomial fitting with well‐defined frequency selectivity. The application of these techniques to a sensor array in the UK is discussed.
Simulations of the magnetosphere for zero interplanetary magnetic field: The ground state

A global MHD simulation code, the Integrated Space Weather Prediction Model, is used to examine the steady state properties of the magnetosphere for zero interplanetary magnetic field. In this “ground state” of the system, reconnection at the magnetopause is absent. Topics reported here include (1) qualitative description of global magnetic field, plasma flow, and current systems (Chapman-Ferraro, geotail, Region 1 and Region 2 currents) (2) quantitative parametric studies of shock jump conditions, magnetopause and shock standoff distance, polar cap voltage, and total Region 1 current for different solar wind speeds and ionospheric Pedersen conductances; and (3) quantitative analysis of the low-latitude boundary layer (LLBL) and its coupling to the ionosphere. The central part of the geomagnetic tail is found to be very long, extending beyond the downstream end of the simulation box at X = −300 RE. Along each flank a “wing-like” region containing closed, albeit strongly stretched, field lines is present. Each such region contains a narrow convection cell, consisting of the tailward flowing LLBL and an adjoining narrow channel of sunward return flow. These cells are the result of viscous-like interaction along the magnetospheric flanks, with an effective kinematic viscosity, entirely of numerical origin, estimated to be ν = 1.8 × 108m2 s−1. Except in certain regions near the magnetopause, the magnetosheath flow is steady and laminar while the internal motion in the tail displays turbulent vortical motion in the plasma sheet. Plasma transport in the tail occurs as a result of this turbulence, and substantial turbulent plasma entry across the equatorial magnetopause is seen in the region −10 RE < X < 0 RE behind the torus of dipolar field lines. The polar cap potential ΔϕPC is 29.9 ± 1.4 kV for VSW = 400 km s−1 and ∑P = 6 mho, which is in reasonable agreement with results inferred from satellite observations. About half of ΔϕPC can be attributed to the LLBLs with the remainder coming from a dawn-to-dusk potential drop along the dayside magnetopause, caused by nonlinearly switched resistivity, added explicitly to the MHD equations, and/or by numerical diffusion. The magnetospheric voltage-current relation at VSW = 400 km s−1 has a constant negative slope with an open circuit voltage of ΔϕPC = 38.5kV. The total Region 1 current (into the northern dawn hemisphere) is 0. 66 MA (at VSW = 400 km s−1 and ∑P = 6 mho). It maximizes at about 2. 83 MA during short-circuit conditions (∑P = ∞; ΔϕPC = 0).
Infected discrete linear systems: on the admissible sources

Let’s consider the discrete system xi+1 = Axi i ≥ 0 and the corresponding output signal yi = Cxi i ≥ 0 Given ϵ≥0 as an index of admissibility, a source e = (ei ) i≥0 is said to beϵ-admissible if is the output function corresponding to the infected system The set of all sources e = (e i ) i≥0 is the admissible set S(ϵ). The characterization of S(ϵ) is investigated and numerical simulations are given. The problem of admissible sources, for discrete delayed systems, is also considered
On the bias of maximum likelihood estimation following a sequential test

SUMMARY Tlhe bias of maximum likelihood estimates calculated at the end of a sequential procedure is investigated. For the two sequential designs considered in detail, the sequential probability ratio test and the triangular test, this bias is appreciable. A method of calculating an adjusted estimate with reduced bias is described, and an approximation to the standard error of the new estimate is provided. Examples of the implementation of the method are given, and its advantages and disadvantages relative to alternative approaches are discussed.
Solvability of Inverse Eigenvalue Problem for Dense Singular Symmetric Matrices

Given a list of real numbers ∧={λ1,…, λn}, we determine the conditions under which ∧will form the spectrum of a dense n × n singular symmetric matrix. Based on a solvability lemma, an algorithm to compute the elements of the matrix is derived for a given list ∧ and dependency parameters. Explicit computations are performed for n≤5 and r≤4 to illustrate the result.
Heavy quark production at the Fermilab Tevatron and DESY ep collider HERA using k(t) factorization with the CCFM evolution approach

The application of k(t) factorization supplemented with the Ciafaloni-Catani-Fiorani-Marchesini (CCFM) small-x evolution equation to heavy quark production at the Fermilab Tevatron and at DESY HERA is discussed. The b (b) over bar production cross sections at the Tevatron can be consistently described using the k(t)-factorization formalism together with the unintegrated gluon density obtained within the CCFM evolution approach from a fit to HERA F-2 data. Special attention is drawn to the comparison with measured visible cross sections, which are compared to the hadron level Monte Carlo generator CASCADE.
Assessment of the Performance of Imputation Techniques in Observational Studies with Two Measurements

: In observational studies with two measurements when the measured outcome pertains to a health related quality of life (HRQoL) variable, one motivation of the research may be to determine the potential predictors of the mean change of the outcome of interest. It is very common in such studies for data to be missing, which can bias the results. Different imputation techniques have been proposed to cope with missing data in outcome variables. We compared five analysis approaches (Complete Case, Available Case, K- Nearest Neighbour, Propensity Score, and a Markov Chain Monte Carlo algorithm) to assess their performance when handling missing data at different missingness rates and mechanisms (MCAR, MAR and MNAR). These strategies were applied to a pre-post study of patients with Chronic Obstructive Pulmonary Disease. We analyzed the relationship of the changes in subjects HRQoL over one year with clinical and socio-demographic characteristics. A simulation study was also performed to illustrate the performance of the imputation methods. Relative and standardized bias was assessed on each scenario. For all missingness mechanisms, not imputing and using MCMC method, both combined with mixed-model analysis, showed lowest standardized bias. Conversely, Propensity Score showed worst bias values. When missingness pattern is MCAR or MAR and rate small, we recommend using mixed models. Nevertheless, when missingness percentage is high, in order to gain sample size and statistical power, MCMC is preferred, although there are no bias differences compared with the mixed models without imputation. For a MNAR scenario, a further sensitivity analysis should be made.
Fabrication of ZnO nanoparticles in SiO2 by ion implantation combined with thermal oxidation

Zinc-oxide (ZnO) nanoparticles (NPs) are fabricated in silica glasses (SiO2) by implantation of Zn+ ions of 60 keV up to 1.0×1017ions∕cm2 and following thermal oxidation. After the oxidation at 700 °C for 1 h, the absorption in the visible region due to Zn metallic NPs disappears and a new absorption edge due to ZnO appears at ∼3.25eV. Cross-sectional transmission electron microscopy confirms the formation of ZnO NPs of 5–10 nm in diameter within the near-surface region of ∼80nm thick and larger ZnO NPs on the surface. Under He–Cd laser excitation at λ=325nm, an exciton luminescence peak centered at 375 nm with FWHM of 113 meV was observed at room temperature.
Lateral-displacement influence on the levitation force in a superconducting system with translational symmetry

The unique properties of superconductors make the design of levitation devices possible. In some of them, lateral displacements of the superconducting levitating part often result in a decrease in the levitation force, which can cause a critical malfunction of the system. In this work, the authors theoretically analyze the levitation force of a system consisting of an infinitely long superconductor over an infinitely long permanent-magnet guideway using a realistic model based on a magnetic-energy minimization procedure, from which they give the physical keys for understanding the levitation force reduction after lateral displacements and how to minimize these effects.
Dielectric properties of heavily doped crystalline and amorphous silicon from 1.5 to 6.0 eV

Extremely uniform, microscopically smooth, large-grained polycrystalline Si films saturation doped with phosphorous to a carrier concentration $n=3.3\ifmmode\times\else\texttimes\fi{}{10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ were prepared by a combination of low-pressure chemical-vapor-deposition and heat-treating processes to obtain samples suitable for measuring the small effects of large impurity concentrations on the above-band-gap dielectric properties of Si. From 1.5 to 2.5 eV, the effects of heavy doping are described by the Drude free-carrier model with lifetimes determined by scattering from lattice vibrations. Above 3 eV, the dielectric function spectrum of heavily doped Si is remarkably similar to that of undoped material except that the ${E}_{1}$ and ${E}_{2}$ structures are broadened and shifted to lower energies. The impurity-induced broadening is much larger for ${E}_{1}$ than for ${E}_{2}$, indicating that a metastable excitonic resonance is well developed for the former but not for the latter. Present and previous data of the authors, together with previous data of Vi\~na and Cardona, are consistent with an approximately linear shift of the threshold energy with impurity concentration. This indicates that the dominant mechanism responsible for the shifts is the effect of the random impurities on the crystal potential. While the possibility of electron-electron and electron-ion interactions on the electron and hole self-energies cannot be ruled out, comparison with recent calculations of Berggren and Sernelius show that these effects must be much smaller at higher interband transitions than at the fundamental indirect band gap. Using our data as a reference, we show that the anomalous absorption observed by Jellison and co-workers for As-implanted and laser-annealed $c\ensuremath{-}\mathrm{S}\mathrm{i}$ is due to microscopically rough surface layers on their samples. Consequently, the differences that they observe between P and As dopants must involve differences in recrystallization and regrowth. Dielectric-function spectra for amorphous Si films doped in situ with phosphorus are essentially identical within microstructural effects to those of undoped material, indicating no significant influence from heavy doping. At energies below 3.2 eV, the data expressed as ${(\ensuremath{\alpha}nE)}^{\frac{1}{3}}$ or as ${({\ensuremath{\epsilon}}_{2})}^{\frac{1}{2}}$ both vary nearly linearly with energy, suggesting nondirect transitions between simple parabolic bands with momentum matrix elements linearly proportional to $E$ or with dipole elements independent of $E$.
Effects of A-Site (NaCe) Substitution with Na-Deficiency on Structures and Properties of CaBi4Ti4O15-Based High-Curie-Temperature Ceramics

Three kinds of bismuth-layer-structured ferroelectric (BLSF) ceramics, CaBi4Ti4O15 (CBT), Ca0.8(CeNa)0.1Bi4Ti4O15 (CNBT), and Na-deficient Ca0.8(Ce0.1Na0.05\Box0.05)Bi4Ti4O15 [CN\BoxBT] (where \Box represents vacancies) were prepared by a conventional ceramic technique. X-ray powder diffraction showed that their crystal structures are a single phase of BLSF with m=4. Sintering characteristics of the three ceramics were also discussed. Scanning electron microscope (SEM) micrographs of CN\BoxBT showed that the grain is platelike. The A-site (NaCe) substitution can improve the piezoelectric constant d33 and high-temperature resistivity with decreasing Curie temperature. The modification by A-site (NaCe) substitution with Na-deficiency is more pronounced than CNBT, which not only leads to a very high piezoelectric constant d33 and high-temperature resistivity but also increases the Curie temperature. The reason for the high Tc (Tc=866°C) of CN\BoxBT is considered to be internal stress. As a result, Na-deficient CN\BoxBT ceramic is found to be an excellent high-temperature piezoelectric material.
Correlated Neutron Emissions from 252Cf

Abstract This paper presents new experimental results of correlated, prompt neutron emission from the spontaneous fission of 252Cf. Specifically, we present correlated-neutron emission probabilities and average energies for two detected neutrons as a function of the angle between the two neutrons. Experimental results are compared to several Monte Carlo models that include the number, energy, and angular distributions of prompt neutrons from fission.
Sources and sinks of zonal momentum in the middle atmosphere diagnosed using the diabatic circulation

Radiative heating rates calculated using monthly mean climatological fields of temperature and ozone are used to diagnose the diabatic circulation in the middle atmosphere. This circulation is then used to infer the zonal force per unit mass. Previous diagnostic studies of the zonal force per unit mass have considered only the northern hemisphere outside the summer period and for heights up to about 60 km. The present study allows calculations for both hemispheres in all seasons at heights up to about 75 km. Strong inter-hemispheric differences in the diagnosed fields are found in the winter and spring hemispheres, whilst the summer and autumn hemispheres are quite similar. The drag on the mean wind in the southern winter mesosphere is found to be up to double that found in the northern winter mesosphere. It is argued that this feature may be due to an enhanced transmission of gravity waves through the southern winter stratosphere; this may, in turn, explain observed inter-hemispheric differences in temperature for the winter months. Differences between the diagnosed fields and those inferred in modelling studies are also discussed. Some attention is also paid to a problem that pervades this and similar studies. The calculated radiative heating rates do not allow a unique diabatic circulation to be diagnosed because of unexplained departures from the global mean mass balance. The diagnosed circulation is thus subject to some uncertainty which puts definite limits on the confidence that can be placed on diagnosed quantities, especially in the stratosphere. It must be recognized that derived quantities are admixtures of the true quantity and imperfections in the data and radiative transfer scheme.
Numerical approximations of darcian flow through unsaturated soil

The choice of appropriate intrablock approximations for the unsaturated hydraulic conductivity is a critical step for the numerical solution of Richards equation. Forms commonly used include arithmetic, geometric and harmonic averaging. The choice is most often based on convenience and custom. This study presents a framework for comparing any scheme for weighting the unsaturated hydraulic conductivity against the correct Darcian flow across a block for steady conditions. Such comparisons are carried out for a number of commonly used averages, and errors are shown to be alarmingly high in some cases. A scheme for approximately matching the correct Darcian flux is illustrated by two infiltration examples. In the first, the arithmetic and weighted schemes are superior to the geometric average when compared to a quasi-analytical solution. For the second example, the weighted solution is slightly better than either the arithmetic or geometric averaging schemes. These examples also illustrate that an acceptable mass balance should not be used as a sole criterion for success as it can probably be attained with most schemes. The conclusions are believed relevant for algorithms which are pressure head based, water content based or other choices and for multidimensional as well as one-dimensional flow problems.
Empirical‐distribution‐function goodness‐of‐fit tests for discrete models

We present a simple framework for studying empirical-distribution-function goodness-of-fit tests for discrete models. A key tool is a weak-convergence result for an estimated discrete empirical process, regarded as a random element in some suitable sequence space. Special emphasis is given to the problem of testing for a Poisson model and for the geometric distribution. Simulations show that parametric bootstrap versions of the tests maintain a nominal level of significance very closely even for small samples where reliance upon asymptotic critical values is doubtful.
Control of Infinite Behavior of Finite Automata

A problem in the control of automata on infinite strings is defined and analyzed. The key to the investigation is the development of a fixpoint characterization of the "controllability subset" of a deterministic Rabin automaton, the set of states from which the automaton can be controlled to the satisfaction of its own acceptance condition. The fixpoint representation allows straightforward computation of the controllability subset and the construction of a suitable state-feedback control for the automaton. The results have applications to control synthesis, automaton synthesis, and decision procedures for logical satisfiability; in particular, they represent a direct, efficient and natural solution to Church's problem, the construction of winning strategies for two-player zero-sum $\omega$-regular games of perfect information, and the emptiness problem for automata on infinite trees.
Noise in the Coulomb blockade electrometer

We have measured the noise of a Coulomb blockade electrometer. Below 100 Hz, the noise referred to the input charge has a 1/f power spectrum with a charge noise of 3×10−4 e/√Hz and an energy sensitivity EN of 3×104 ℏ at 10 Hz. The 1/f noise probably results from the stochastic occupation of charge traps which could in principle be eliminated. The theoretical noise floor is set by shot noise, and indirect measurements show that this contribution to EN can be as small as 1.5 ℏ, suggesting that the electrometer will be a quantum limited amplifier if the 1/f noise can be eliminated.
Tornado Warnings, Lead Times, and Tornado Casualties: An Empirical Investigation

Abstract Conventional wisdom holds that improved tornado warnings will reduce tornado casualties, because longer lead times on warnings provide extra opportunities to alert residents who can then take precautions. The relationship between warnings and casualties is examined using a dataset of tornadoes in the contiguous United States between 1986 and 2002. Two questions are examined: Does a warning issued on a tornado reduce the resulting number of fatalities and injuries? Do longer lead times reduce casualties? It is found that warnings have had a significant and consistent effect on tornado injuries, with a reduction of over 40% at some lead time intervals. The results for fatalities are mixed. An increase in lead time up to about 15 min reduces fatalities, while lead times longer than 15 min increase fatalities compared with no warning. The fatality results beyond 15 min, however, depend on five killer tornadoes and consequently are not robust.
Experimental demonstration of high quality factor, x-dipole modes in InAs∕InP quantum dot photonic crystal microcavity membranes

The authors study the quality factor Q of the x-dipole mode in single missing hole defect photonic crystal microcavities in InAs∕InP quantum dot membranes as a function of the structural design parameters. Photoluminescence experiments show an optimized Q in excess of 28 000 for a wavelength close to λ=1550nm. This is to be compared with a Q of 57 000 determined by finite difference time domain calculations. The fabrication tolerances necessary to achieve experimental Q values close to those predicted by theory are identified.
Empirical Modeling of Layered Integrated Water Vapor Using Surface Mixing Ratio in Nigeria

Abstract Using the available upper-air data for three stations in Nigeria (Lagos, a coastal station; Minna, an inland station; and Kano, a sub-Sahelian station), an intensive examination has been carried out on the linkage between surface mixing ratio rs and layered integrated water vapor W (g cm−2) over Nigeria. The goal was to identify the seasonal distribution of the parameter and to develop models that can best be used to estimate W from surface mixing ratio. To achieve these objectives, integrated water vapor at the low level (WL), midlevel (Wm), and upper level (Wu) and total column integrated water WT have been calculated using daily values of upper-air data spanning over a decade from the above three radiosonde stations. A relationship of the form W = αrs + β (where α and β are constants) has been established between W and rs using the analysis-of-variance (ANOVA) technique. Tests carried out on the models, using daily soundings made in 1990 for Lagos, 1983 for Minna, and 1991 for Kano, respective.
Nodal Expansions. Distribution Functions, Potentials of Average Force, and the Kirkwood Superposition Approximation

The customary density power series expansions of potentials of average force and distribution functions are converted into a new class of expansions, defined in terms of topological nodes. The physical meaning of the terms in the new expansions is discussed, and arguments are presented to show that the new expansions can be expected to converge considerably more rapidly than the customary density expansions. The probable occurrence of phase transitions is discussed. Possible further developments are suggested. The Kirkwood superposition approximation is shown to be valid for a large number of terms in the expansions of potentials of average force and distribution functions. The customary comparison of the exact value of the third virial coefficient with that obtained via the Kirkwood superposition approximation is shown to provide no proof of the validity or invalidity of the latter.
Transient flow around an impulsively started cylinder using a dynamic mesh method

The finite volume method (FVM) with a dynamic mesh method (DMM) to deal with the moving boundary was applied to the simulation of two-dimensional incompressible viscous flow past a circular cylinder that is impulsively started into rotation and translation. The non-dimensional rotating to translating speed ratio α is varied from 0.28 to 2.07, with the Reynolds number being 200 for the range of α. The computation covers a period, during which the cylinder translates seven times its diameter. The current scheme handles the impulsively moving boundary directly by DMM, which is implemented using both mesh deforming and local remeshing. The instantaneous asymmetrical flow configurations for various α are presented and compared with the experimental visualizations. Quantitatively, the velocity distributions with drag and lift coefficients are also compared with the experimental and numerical results. Results show that the flow is strongly influenced by the rotation. Comparisons are found to be satisfactory.