Miracle-dz/UniFAR-FTUs huggingface dataset:
Scattering of electrons at threading dislocations in GaN

A model to explain the observed low transverse mobility in GaN by scattering of electrons at charged dislocation lines is proposed. Filled traps along threading dislocation lines act as Coulomb scattering centers. The statistics of trap occupancy at different doping levels are investigated. The theoretical transverse mobility from Coulomb scattering at charged traps is compared to experimental data. Due to the repulsive potential around the charged dislocation lines, electron transport parallel to the dislocations is unaffected by the scattering at charged dislocation lines.
A HIGH-RESOLUTION PHOTOIONIZATION STUDY OF 56Fe USING A VACUUM ULTRAVIOLET LASER

The photoionization efficiency (PIE) spectrum for 56Fe formed by laser ablation has been measured using tunable vacuum ultraviolet (VUV) laser radiation in the energy range of 63000–74700 cm−1, covering the threshold regions for the photoionization transitions of Fe+(3d64s 6D) ← Fe(3d64s2 5D) and Fe+(3d64s 4D) ← Fe(3d64s2 5D). The fact that no step-like structures in the PIE spectrum are observed at these ionization thresholds indicates that direct photoionization plays a very minor role in the photoionization of Fe in this VUV energy range. Comparing the VUV-PIE and the VUV-absorption spectra of Fe shows that all prominent absorption bands of Fe correspond to strong autoionizing structures in the PIE spectrum of Fe. Due to the significantly narrower VUV laser optical bandwidth of 0.12 cm−1 used in the present study, complex autoionizing resonances are resolved in the PIE spectrum. Two autoionizing Rydberg series (3d7 4F7/2)np (n = 9–27) and (3d7 4F9/2)np (n = 10–32) formed by two-electron excitations from the (3d64s2 5D4) ground state are identified to converge to the respective Fe+(3d7 4F7/2) and Fe+(3d7 4F9/2) ion levels. The photoionization cross sections and well resolved autoionizing Rydberg resonances observed in this study are relevant to astrophysics for understanding the Fe contribution to the VUV opacity in the solar atmosphere, and for benchmarking theoretical calculations under the Opacity Project and the IRON Project.
Spectral Properties of Preconditioned Rational Toeplitz Matrices

Various Toeplitz preconditioners $P_N $ have recently been proposed so that an $N \times N$ symmetric positive definite Toeplitz system $T_N {\bf x} = {\bf b}$ can be solved effectively by the preconditioned conjugate gradient (PCG) method. It has been proven that if $T_N $ is generated by a positive function in the Wiener class, the eigenvalues of the preconditioned matrices $P_N^{ - 1} T_N $ are clustered between $( 1 - \epsilon ,1 + \epsilon )$ except for a fixed number independent of N. In this research, the spectra of $P_N^{ - 1} T_N $ are characterized more precisely for rational Toeplitz matrices $T_N $ with preconditioners proposed by Strang [Stud. Appl. Math., 74 (1986), pp. 171–176] and Ku and Kuo [IEEE Trans. Signal Process. , 40 (1992), pp. 129–141]. The eigenvalues of $P_N^{ - 1} T_N $ are classified into two classes, i.e., the outliers and the clustered eigenvalues, depending on whether they converge to 1 asymptotically. It is proved that the number of outliers depends on the order of the rat.
Dependence of the dayside magnetopause reconnection rate on local conditions

We estimate the reconnection rates for eight dayside magnetopause reconnection events observed by the Cluster spacecraft and compare them with the predictions of the Cassak‐Shay Formula (Rcs) Cassak and Shay (2007). The measured reconnection rate is determined by calculating the product of the inflow velocity and magnetic field in the magnetosheath inflow region. The predicted reconnection rate is calculated using the plasma parameters on both sides of the current layer, including the contributions of magnetosheath H+, magnetospheric hot H+ and O+, and magnetospheric cold ions. The measured reconnection rates show clear correlations with Rcs with an aspect ratio of 0.07. The O+ and cold ions can contribute up to ~30% of the mass density, which may reduce the reconnection rate for individual events. However, the variation of the reconnection rate is dominated by the variation of the magnetosheath parameters. In addition, we calculated the predicted reconnection rate using only magnetosheath parameters (Rsh). The correlation of the measured rate with Rsh was better than the correlation with Rcs, with an aspect ratio of 0.09. This might indicate deviations from the Cassak‐Shay theory caused by the asymmetric reconnection structure and kinetic effects of different inflow populations. A better aspect ratio is expected to be between the ones determined using Rcs and Rsh. The aspect ratio does not show a clear dependence on the O+ concentration, likely because the O+ contribution is too small in these events. The aspect ratio also does not show a clear correlation with density asymmetry or guide field.
Understanding unit rooters: a helicopter tour

For the first-order univariate autoregression without constant term, the joint density (corresponding to a flat prior) for the true coefficient and its least squares estimate is estimated by Monte Carlo and graphically displayed. The graphs show how a symmetric distribution for the coefficient conditional on the estimate coexists with an asymmetric distribution for the estimate conditional on the coefficient. Prior densities implicit in treating classical significance levels as if they were Bayesian posterior probabilities are calculated. They are shown to depend sensitively on the estimated coefficient and to put substantial probability on values of the coefficient above one. Copyright 1991 by The Econometric Society.
Inharmonicity of Plain Wire Piano Strings

The inharmonicity of plain wire strings in situ has been measured in six pianos of various styles and makes. By inharmonicity is meant the departure in frequency from the harmonic modes of vibration expected of an ideal flexible string. It is shown from the theory of stiff strings that the basic inharmonicity cents (hundredths of a semitone) is given by 3.4×1013n2d2/v02l4, where n is the mode number, d is the diameter of the wire in cm, l is the vibrating length in cm, and v0 is the fundamental frequency. A value of Q/ρ = 25.5 × 1010 (cm/sec)2 was assumed for the steel wire, where Q is Young's modulus and ρ is the density. The observations are entirely compatible with the relationship given. In general terms the inharmonicity of the plain steel strings is about the same in all the pianos tested, being about 1.2 cents for the second mode of vibration of the middle C string. Above this point every eight semitones it is doubled. Below middle C the inharmonicity is consistently less in large pianos than in sm.
39—The Fitting of Woven Cloth to Surfaces

The possible configurations adopted by woven cloth when fitted to various surfaces are discussed in this paper. A general type of fitting (involving two parameters) to surfaces of revolution is given together with some photographic illustrations. The differential equations of fitting to any surface are derived and it is found that the general type of fitting is the only type which is expressible by formulae and which has generality.
Characteristics of tropical cyclone activity over the eastern North Pacific: the extremely active 1992 and the inactive 1977

Abstract The eastern North Pacific experiences large variability in tropical cyclone (tropical storm and hurricane) frequency from year to year. Large-scale environmental conditions during the peak hurricane season (July, August and September) are contrasted for two extreme years; 1992 is the most active year and 1977 the most inactive year. Sea surface temperatures in both 1992 and 1977 arewarm and favourable for tropical cyclone (TC) formation, whereas other environmental factors undergo pronounced changes over the major development area (MDA) for the two extreme years. For instance, the 1992 hurricane season features weaker vertical wind shear, larger low-level relative vorticity, stronger mid-tropospheric ascending motion, stronger upper-level divergence, and larger mid-tropospheric moisture content than the 1977 hurricane season. These changes correspond well to the variation of the TC activity during the two extreme years. In addition, a monsoon trough is only present over the MDA in 1992. Convective disturbances within a 4–10-d period propagating consistently from the east bring stronger convection in 1992 than in 1977. In both years, anomalous zonal wind over the MDA oscillates with the intraseasonal timescale. However, TCs do not necessarily form during the westerly phases in either year in the intraseasonal timescale.
Wigner model for Klein tunneling in graphene

Quantum corrections to the electron-hole motion in graphene are investigated by applying the multiband Wigner approach. A diagonalization procedure regarding the pseudo-spin degree of freedom is proposed. The resulting formulation of the equation of motion reveals to be particularly close to the classical description of the particle motion. This formal analogy offers a framework in which quantum phenomena can be described with a classical language and the question of the quantum-classical correspondence can be directly investigated. Some numerical results are presented showing the ability of our quasi-diagonal Wigner model to reproduce Klein tunneling in graphene under the application of an external electric field.
Finiteness of compact maximal flats of bounded volume

Let M be a complete Riemannian locally symmetric space of non-positive curvature and of finite volume. We show that there are only finitely many compact maximal flats in M of volume bounded by a given number. As a corollary in the case $M=\mathrm{SL}_n(\mathbb{Z})\backslash\mathrm{SL}_n(\mathbb{R})/\mathrm{SO}_n$, we give a different proof of a theorem of Remak that for any $n\in \mathbb{N}$, there are only finitely many totally real number fields of degree n whose regulator is less than a given number.
Wind variability in the large Magellanic cloud B[e] supergiant HD 34664

We present optical linear spectropolarimetry of the B(e) supergiant HD 34664. The polarization and position angle display significant spectral features which correspond to the H-alpha and H-beta emission lines. We use the line polarizations to separate the interstellar foreground polarization from the intrinsic polarization of HD 34664. The intrinsic polarization is consistent with electron scattering in a circumstellar disk seen at high inclination and provides further and independent evidence for the two-component wind model of the B(e) supergiants. We compare the polarization and spectrum of HD 34664 to observations published in the literature. In our data the continuum polarization is by a factor of two larger and the H-alpha line-to-continuum ratio is by a factor of at least four increased over previous observations. Since both the polarization and the line intensity are measures of the electron density in the stellar wind, we suggest that the observed variations can be attributed to a rise in the stellar mass-loss rate.
A Comprehensive Model for Nucleate Pool Boiling Heat Transfer Including Microlayer Evaporation

The results of an experimental investigation are presented in which dichloromethane (methylene chloride) boiling on a glass surface was studied using laser interferometry and high-speed photography. New data for active site density, frequency of bubble emission, and bubble departure radius were obtained in conjunction with measurements of the volume of microlayer evaporated from the film underlying the base of each bubble for various combinations of heat flux and subcooling. These results were used to support a model for predicting boiling heat flux incorporating microlayer evaporation, natural convection, and nucleate boiling mechanisms. Microlayer evaporation heat transfer is shown to represent a significant proportion of the total heat transfer for the range of heat flux and subcooling investigated.
High amplitude steady streaks in flat plate boundary layers

This experimental activity is part of a large research program aimed at developing a passive control method for viscous drag reduction of aerodynamic bodies. The drag reduction, accomplished by delaying the laminar-turbulent transition of the boundary layer, is obtained by generating stable laminar streamwise streaks inside the boundary layer, which are known to stabilize the growth of Tollmien-Schlichting waves as well as localized disturbances. A first series of experiments have shown that by means of suitable roughness elements it is possible to generate stable steady streaks of amplitudes up to 12% of the free stream velocity. In this paper we explore the possibility to generate streaks of much larger amplitude by using a row of Miniature Vortex Generators (MVGs). Experiments have been performed showing that amplitudes up to 30% can be obtained without having any secondary instability acting on the streaks. The induced drag due to the streaky base flow is quantified and it is demonstrated that the streaks can be reinforced by placing a second array of MVGs downstream of the first one.
Analytical Solutions for the Modeled k Equation

The semitheoretical function of Nezu and Nakagawa (1993, Turbulence in Open-Channel Flows, A. A. Balkema, ed., Rotterdam, The Netherlands) for the turbulent kinetic energy k is valid only where local equilibrium is a good approximation. From an estimation of the difference between the energy production and its dissipation G-E, we present in this study an analytical solution for the modeled k equation. Comparisons with direct numerical simulation data of turbulent channel flows show good agreement. A universal function for k + is deducted for y + <20.
Pressure-induced Softening of Shear Modes in ZnO

The room-temperature elastic moduli C{sub IJ} corresponding to the pure longitudinal and transverse modes in single crystals of the wurtzite phase of ZnO have been determined from ultrasonic wave velocities measurements as a function of pressure up to 10 GPa. All the moduli exhibit a linear dependence on pressure, with positive values for the longitudinal moduli (dC{sub 11}/dP=5.32 and dC{sub 33}/dP=3.78) but negative values for the shear moduli (dC{sub 44}/dP={minus}0.35 and dC{sub 66}/dP={minus}0.30). All modes exhibit anomalous travel time above P{sub Tr}=7.5GPa, indicating the onset of a transition to the rocksalt (B1) phase. Using recent improvements for ultrasonic measurements in multianvil apparatus, this experimental study on the phase-transformation mechanism is extended to simultaneous high pressures and high temperatures. At high temperatures, P{sub Tr} decrease and the pressure derivatives of the elastic shear modes become more negative. Thus, the elastic shear softening observed at room temperature is enhanced at elevated temperatures.
Constitutive modeling of dense gravelly soils subjected to cyclic loading

A constitutive model for dense gravelly soils was developed to reproduce their responses under cyclic loadings. Its application aims at nonlinear dynamic analyses of earth structures involving gravelly soils, such as rockfill dams and railroad ballasts. The framework of generalized plasticity was modified to incorporate the concept of stress distance for better simulation of unloading and reloading responses. It was then combined with the theory of critical state soil mechanics to develop the constitutive model. The model has the following important features: unified simulation of particle breakage through translating critical state line, smooth transition from unloading to reloading in the stress space, and proper modeling of cyclic hysteresis, cyclic densification, and cyclic hardening of dense gravelly soils. Most of the model parameters can be obtained through simple calculation using conventional triaxial test results, and their calibration process was discussed. The model was used to simulate the cyclic responses of three gravelly soils with satisfactory accuracy. Copyright © 2014 John Wiley & Sons, Ltd.
On topologically realizing modules over the Steenrod algebra

The mod p cohomology of a space or spectrum X is a module over the mod p Steenrod algebra A. If X is a space, it has additional structure making it an unstable A-algebra, where we recall that an A-module M is unstable if, when p = 2, Sqi x = 0 for all i > IxI and x E M, and, when p > 2, 3ePix = 0 for all 2i + e > JxJ, e = 0 or 1, and x E M. Questions about realizing particular A-modules, algebras, and A-algebras as the cohomology of spaces or spectra are among the most fundamental in algebraic topology. The Hopf invariant one problem [A] and the problem of realizing polynomial algebras [DMW] are two famous examples of ongoing interest. If one regards the first of these as a problem about realizing finite A-modules, and the second of these as a problem about realizing rather large A-modules, it is the purpose of this paper to study the "middle ground". We begin with the following conjecture.
Reduction of speckle noise in digital holography by multiple holograms

In this paper, we introduce and demonstrate a new method of reducing speckle noise by multiply holograms. It can utilize both the phase and amplitude information of the object wave-front. In the superposition process, the phase surfaces with high signal to noise ratio in the different phase images have been appropriately weighted according to reconstructed intensity image. We show a theoretical justification of the procedure and experimentally-obtained results of a USAF-1951 resolution test target, both of which demonstrate that the proposed method could reduce the speckle noise effectively, and improve the resolution of reconstructed image.
Time-of-Day-Dependent Effects of Monochromatic Light Exposure on Human Autonomic Nervous System

We report the time-of-day-dependent effects of monochromatic lights at wavelength of 458 nm and 550 nm on human physiological and psychological parameters under the same irradiance density (9.8 µW/cm2 at eye level). We conducted an experiment in the daytime and nighttime on different days. Twelve subjects were selected, none of whom was either a morning-type or evening-type person, as assessed by the morningness/eveningness questionnaire. We found that 458 nm light exposure caused a greater high-frequency (HF)/(HF+low-frequency (LF)) component than did 550 nm light. The change of oral temperature (ΔTor) during exposure to 458 nm light was larger than that to 550 nm light in the daytime. Our findings indicate that short-wavelength monochromatic light can affect the circadian rhythms of autonomic nerve function and body temperature.
Interstellar CH3CCD

We report the detection of a new interstellar molecule: CH3CCD, a deuterated isotopomer of methyl acetylene. Analysis of lines detected at seven positions along the ridge of the dark cloud TMC-1 indicates that the CH3CCD column density and fractionation exhibit strong spatial gradients, with D/H ratios ranging from a minimum of 0.04 at the cyanopolyyne peak (CP) position to as high as 0.18. We find that the column density in CH2DCCH is almost constant along the ridge, whereas that of CH3CCD increases and that of CH3CCH decreases in moving away from the CP. Chemical mechanisms that may explain the observed fractionation trends in CH3CCD and CH2DCCH are briefly discussed.
LMI Approach to Output Feedback Stabilization for Fuzzy Systems with Immeasurable Premise Variables

This paper is concerned with output feedback control design for a fuzzy system with immeasurable premise variables. It is well known that Takagi-Sugeno fuzzy model describes a wide class of nonlinear systems especially when its premise variables include immeasurable functions. However, when it comes to control design of such a fuzzy system with immeasurable premise variables, a conventional parallel distributed compensator (PDC) is not feasible because it shares the same premise variables as those of a fuzzy system. In this paper, we introduce an output feedback controller with the estimate of the premise variables of an original fuzzy system. We then formulate the stabilization problem for a fuzzy system with immeasurable premise variables. Our control design method is based on a set of strict LMI conditions. No tuning parameter is necessary a priori to solve LMI conditions. Our method includes tuning matrices for control gains in a controller and hence they can be chosen to optimize the control performance of the system. Numerical examples are finally given to illustrate our control design method.
Stellar Spectropolarimetry with Retarder Waveplate and Beam Splitter Devices

Nighttime polarimetric measurements are often obtained very close to the limits of the instrumental capabilities. It is important to be aware of the possible sources of spurious polarization, and to adopt data reduction techniques that best compensate for the instrumental effects intrinsic to the design of the most common polarimeters adopted for nighttime observations. We define a self-consistent framework starting from the basic definitions of the Stokes parameters, and we present an analytical description of the data reduction techniques commonly used with a polarimeter (consisting of a retarder wave plate and a Wollaston prism) to explore their advantages and limitations. We first consider an ideal polarimeter in which all optical components are perfectly defined by their nominal characteristics. We then introduce deviations from the nominal behavior of the polarimetric optics, and develop an analytical model to describe the polarization of the outgoing radiation. We study and compare the results of two different data reduction methods, one based on the differences of the signals, and one based on their ratios, to evaluate the residual amount of spurious polarization. We show that data reduction techniques may fully compensate for small deviations of the polarimetric optics from their nominal values, although some important (first-order) corrections have to be adopted for linear polarization data. We include a detailed discussion of quality checking by means of null parameters. We present an application to data obtained with the FORS1 instrument of the ESO VLT, in which we have detected a significant amount of cross talk between circular and linear polarization. We show that this cross-talk effect is not due to the polarimetric optics themselves, but is most likely caused by spurious birefringence due to the instrument’s collimator lens.
From Restricted Weak Type to Strong Type Estimates

Let T be a sublinear operator such that (TχE)*(t) ⩽ h(t, |E|) for some positive function h(t,s) and every measurable set E. Then it is shown that under some conditions on the operator T, this restricted weak type estimate can be extended to the set of all functions f∈ L1 such that ‖f‖∞⩽ 1, in the sense that (Tf)*(t)⩽ h(t, ‖f‖1). This inequality allows strong type estimates for T to be obtained on several classes of spaces, such as logarithmic spaces and Lorentz spaces. A similar problem for operators T acting on radial functions is also studied.
Error Estimation in Wind Fields Derived from Dual-Doppler Radar Measurement

Abstract Variance in horizontal and vertical winds are predicted when these components are computed from dual-Doppler velocity measurements combined with terminal velocity estimates and the continuity equation. Errors in horizontal wind magnitude and direction are shown to be functions of wind direction and speed as well as spatial location. Vertical wind could be estimated with errors less than a few meters per second up to altitudes near 14 km over a region 4d × 4d, where 2d is the radar separation. Vertical wind variance at high altitudes is related to accumulation of errors due to the integration of the continuity equation. The cause of wind variance is assumed to be uncertainty in mean Doppler velocity estimates produced by spectrum broadening mechanisms (e.g., shear, turbulence). Two interpolation methods, used to estimate Doppler velocity at common grid locations, are compared and their contribution to Doppler velocity variance reduction is calculated. Terminal velocity variance has been related to.