Miracle-dz/UniFAR-FTUs huggingface dataset:
Amortized Computational Complexity

A powerful technique in the complexity analysis of data structures is amortization, or averaging over time. Amortized running time is a realistic but robust complexity measure for which we can obtain surprisingly tight upper and lower bounds on a variety of algorithms. By following the principle of designing algorithms whose amortized complexity is low, we obtain “self-adjusting” data structures that are simple, flexible and efficient. This paper surveys recent work by several researchers on amortized complexity.
Creep characterization of superalloy IN-738 using ultrasonic nonlinearity measurement

The higher harmonic generation technique has been presented to investigate the creep characteristics of nickel-based superalloy. The primary γ′ precipitates became coarsened preferentially in the direction perpendicular to the applied stress axis during the creep deformation and the Vickers hardness decreased with creep time due to loss of interfacial strain between γ matrix and γ′ precipitate. The increase in ultrasonic nonlinearity with increasing creep time is discussed in relation to the directional coarsening of the γ′ precipitates, which was closely related to the scattering and distortion of the ultrasonic wave.
Monotonicity of the Power Functions of Some Tests of Independence between Two Sets of Variates

1. Summary. For testing independence between two sets of normally distributed variates we consider the class of test procedures which are invariant under certain groups of transformations and depend only on the sample canonical correlation coefficients [1]. The power function of such a test depends only on the population canonical correlation coefficients as parameters, which may be regarded as measures of deviation from the hypothesis. In this paper sufficient conditions on the invariant procedure for the power function to be a monotonically increasing function of each of the parameters are obtained. The likelihood-ratio test [1] and Roy's maximum root test [5] satisfy these conditions. In [4] only the unbiasedness of the maximum root test was proved, although the authors claimed to prove the monotonicity property.
AlGaN/GaN high electron mobility transistors with nickel oxide based gates formed by high temperature oxidation

We report on the design of gates of AlGaN/GaN high electron mobility transistors (HEMTs) to be predetermined for high temperature applications. In this design, nickel oxide (NiO) gate interfacial layer is formed by high temperature oxidation (T = 500–800 °C, for 1 min) of 15 nm thick Ni gate contact layer to provide a high temperature stable gate interface. AlGaN/GaN HEMTs with thermic NiO gate contact layer show excellent dc performance with higher peak transconductance, larger gate voltage swing, higher linearity, and thermal stability as compared to the reference device based on Ni gate contact layer.
A survey of ionospheric effects on space-based radar

Abstract In this survey, we fully review almost all potential ionospheric effects on the performance of space-based radar systems (SBRs), which operate in the ambient ionosphere environment; in particular, we review the use of space-based synthetic aperture radar systems (SARs) for imaging. There are two families of effects involved. One is the effects of the background ionosphere (non-turbulent ionosphere), such as dispersion, group delay, refraction, Faraday rotation, and phase shift. The other is the effects due to ionospheric irregularities, such as refractive index fluctuation, phase perturbation, angle-of-arrival fluctuation, pulse broadening, clutter, and amplitude scintillation. These effects adversely affect SAR imaging in several respects, such as by causing image shift in the range, and degradations of the range resolution, azimuthal resolution, and/or the resolution in height (elevation). We also review ionospheric irregularity characteristics and descriptions, propagation channel statistics, received signal statistics, and detection performance of SBRs in ionospheric scintillation situations. First, a brief outline of SBR systems and principles, and theories of wave propagation in random media, especially some effects caused by two-way propagation, is given. Finally, several of the most probable directions of future research are pointed out.
Materials, Fabrication, and Manufacturing of Micro/Nanostructured Surfaces for Phase-Change Heat Transfer Enhancement

This article describes the most prominent materials, fabrication methods, and manufacturing schemes for micro- and nanostructured surfaces that can be employed to enhance phase-change heat transfer phenomena. The numerous processes include traditional microfabrication techniques such as thin-film deposition, lithography, and etching, as well as template-assisted and template-free nanofabrication techniques. The creation of complex, hierarchical, and heterogeneous surface structures using advanced techniques is also reviewed. Additionally, research needs in the field and future directions necessary to translate these approaches from the laboratory to high-performance applications are identified. Particular focus is placed on the extension of these techniques to the design of micro/nanostructures for increased performance, manufacturability, and reliability. The current research needs and goals are detailed, and potential pathways forward are suggested.
On Asymptotically Lacunary Σ-Statistical Equivalent Sequences Of Fuzzy Numbers

This paper presents the asymptotically lacunary σ-statistical equivalent which is a natural combination of the definition for asymptotically equivalent, invariant mean and lacunary statistical convergence of fuzzy numbers. In addition, we shall also present asymptotically lacunary σ-statistical equivalent analogs of Savas and Nuray's theorems in Ref. 8.
Electron dynamics in two‐ and one‐dimensional oblique supercritical collisionless magnetosonic shocks

Two- and one-dimensional fully electromagnetic, bounded, particle (for both electrons and ions) codes are used in order to study electron dynamics in collisionless magnetosonic shocks propagating in supercritical regime and quasi-perpendicular direction (90° > θ0 > 45°); θ0 is the angle between the shock normal and the upstream magnetic field. The purpose of the study consists in comparing electrons behavior in one-dimensional (“pseudo-oblique”) nonresistive shocks and in two-dimensional resistive oblique shocks. Resistive effects related to plasma microinstabilities can be self-consistently included in two-dimensional particle codes in contrast with one-dimensional particle codes. Present two-dimensional results reproduce local electron distribution functions (in particular, downstream “flat tops”) in a self-consistent way and in good agreement with observational results. On the other hand, one-dimensional results exhibit either local enlarged Maxwellian distributions with a partial tail, or a flat top distribution according to the particle density n. These results emphasize that (1) the differences observed between one- and two-dimensional codes may be explained in terms of a critical particle density nc used in the one-dimensional code; (2) the evidence of flat tops in both two- and one-dimensional results (provided that n > nc) proves that the macroscopic potential jump at the shock front is mainly responsible for their formation; (3) microscopic effects (herein related to the self-consistent cross-field/field-aligned currents instabilities) may represent a complementary mechanism for filling the flat top distribution; (4) some relaxation of the unstable electron flat top distribution (T∥/T⊥ ≫ 1) is observed when penetrating further into the downstream region, which means that the main filling mechanisms are localized in the ramp of the shock. Moreover, a detailed study of two-dimensional results shows that both resistive and nonresistive configurations can be easily distinguished for θ0 ≈ 90°, but not any more for large deviations of θ0 from 90° for which the self-consistent magnetic field rotates noticeably out of the coplanarity plane at the shock front.
The Cessation of Eclipses in SS Lacertae: The Mystery Solved

The 14.4 day period eclipsing binary SS Lacertae in the open cluster NGC 7209 is unusual in that the eclipses stopped completely about the middle of this century, giving rise to considerable speculation as to the cause. Disruption of the binary through a collision with another member of the cluster and, more likely, gravitational perturbations from a third star in the system have been proposed to explain the phenomenon. We present here the results of our intensive radial velocity monitoring of the object, which show clearly that there is indeed a third star in the system in a slightly eccentric orbit with a period of about 679 days. We also reanalyze the historical light curves of SS Lac to determine the properties of the system early in the century. We discuss the implications of our findings in terms of changes in the inclination angle of the close pair. An analysis of available times of eclipse for SS Lac together with the new velocity information has also revealed apsidal motion in the system, = 0. °0137 cycle-1, corresponding to an apsidal period of about 1000 yr. We argue that the third star is probably responsible for this effect also.
Ionisation of highly excited atoms by electric fields. III. Microwave ionisation and excitation

The Monte-Carlo classical trajectory method is used to obtain the probability for microwave ionisation of atoms in states n approximately=66 in agreement with the experiments of Bayfield and Koch (1974). In addition the method displays the time evolution of excitation and ionisation processes and shows that the latter may proceed through a great variety of intermediate excitation processes. The mechanism is discussed. The probability of ionisation at time t is given by Pion(t)=(1-QT)(1-exp(- beta (t)t)) where QT is the probability of orbits which lie in invariant tori. Quantal effects are not significant for comparison with the Bayfield and Koch experiment, but they are discussed in connection with the implications of the results for multiphoton laser ionisation of low n states.
Globally coupled multiattractor maps: Mean field dynamics controlled by the number of elements

We report an investigation of a system of N globally coupled maps able to support multiattractors. For these systems the mean field dynamics is controlled by the number of elements in the initial partition of each basin of attraction. This behavior is in strong contrast with coupled systems of maps with a single attractor, where the mean field dynamics is usually simple for weak couplings. In spite of the increased local complexity, the global dynamics can be reduced to a simple two-dimensional map up to the first bifurcation point of the coexisting attractors. @S1063-651X~99! 50601-6#
Estimating multiple-input– multiple-output production functions with an analysis of credit unions

In this article, we develop a methodology to estimate production functions characterized by multiple inputs and multiple outputs. Aggregate output is estimated assuming a piecewise-linear production possibility set and by measuring distance to the boundary using nonparametric techniques. The parameters of the production function are then estimated in a second-stage using Ordinary Least Squares (OLS). The primary advantage of this approach is the ability to measure the output aggregate nonparametrically. The approach developed in this article is applied to estimate credit union production. An alternative approach developed by Vinod (1968) specifies an extended Cobb–Douglas equation and estimates the parameters using canonical correlation. Our new approach is compared to Vinod's canonical correlation approach.
Wavelet-based SAR images despeckling using joint hidden Markov model

In the past few years, wavelet-domain hidden Markov models have proven to be useful tools for statistical signal and image processing. The hidden Markov tree (HMT) model captures the key features of the joint probability density of the wavelet coefficients of real-world data. One potential drawback to the HMT framework is the deficiency for taking account of intrascale correlations that exist among neighboring wavelet coefficients. In this paper, we propose to develop a joint hidden Markov model by fusing the wavelet Bayesian denoising technique with an image regularization procedure based on HMT and Markov random field (MRF). The Expectation Maximization algorithm is used to estimate hyperparameters and specify the mixture model. The noise-free wavelet coefficients are finally estimated by a shrinkage function based on local weighted averaging of the Bayesian estimator. It is shown that the joint method outperforms lee filter and standard HMT techniques in terms of the integrative measure of the equivalent number of looks (ENL) and Pratt's figure of merit(FOM), especially when dealing with speckle noise in large variance.
Determination of the width of the carrier recombination zone in organic light-emitting diodes

Bilayer organic light-emitting diodes based on tris-(8-hydroxyquinolinato) aluminum III have been fabricated where the thickness of the light-emitting layer was varied between 10 and 80 nm while maintaining a constant total thickness of the organic layers. The electroluminescence quantum efficiency of the devices was measured as a function of the emitter thickness, and used to determine the width of the carrier recombination zone at different electric fields. The width of the carrier recombination zone is found to decrease with an increase in electric field [from 70 nm (E=0.75 MV/cm) to 40 nm (E=1.0 MV/cm)]. It is also related to the field-dependent carrier injection efficiency. An estimate of the light output coupling factor (0.4) is also given based on this analysis.
A full wave solution for propagation in multilayered viscoelastic media with application to Gaussian beam reflection at fluid–solid interfaces

A new solution technique for wave propagation in horizontally stratified viscoelastic media is presented. The model provides a full wave solution for the field generated by a single source as well as for that generated by a vertical source array. It allows the spatial distribution of the acoustic field to be evaluated at least one order of magnitude faster than with existing models based on the Thomson–Haskell solution technique. The computational efficiency of the numerical code is demonstrated by providing exact numerical solutions for the reflectivity pattern associated with narrow ultrasonic beams incident on a fluid–solid interface near the Rayleigh angle.
Frequency, Amplitude, and Waveform Modulation in the Vocal Vibrato

Various observers have noted that the fluctuation of pitch in the normal vocal vibrato is accompanied by a fluctuation of loudness and of timbre. Although this coupling is an implicit outgrowth of the formant principle, the point does not appear to have been explicitly pointed out in the literature, and seems to have been missed by some. Consider any single partial lying on the slope of a resonance peak, such as a vowel formant. If the slope is positive, an increase in frequency leads to an increase in intensity; if negative, the converse is true. Since the voice has many partials randomly located with respect to the formants, the loudness may be expected to vary with pitch, but with sometimes a positive and sometimes a negative phase relation. The overtone structure will also vary though the vibrato cycle. This timbre vibrato is clearly shown in a motion picture made some years ago at Bell Telephone Laboratories. Several other interesting points concerning the practical utility of the vibrato in singing .
Statistical Approaches Applied on a Greek Lip Cancer Dataset

Having at our disposal a dataset of 186 lip cancer cases in Greece, we attempt to interpret them by applying four different statistical methods: Generalized Linear Model (GLM), Markov Chain Monte Carlo (MCMC), Cox proportional hazards model and Bayes factor. The likelihood score equations from GLM exerted estimators with bounded influence, so that the resulting estimators were robust against outliers while maintaining high efficiency in the absence of outliers. Batch means method of estimating the variance of the asymptotic normal distribution, used in MCMC, gave strong consistency when it was applied to our data. A Cox proportional hazards model done with a weighted expectation-maximization gave efficient parameter estimates. Finally, using Bayes factor to the prior distributions for the parameters in compared regression models was proved to be highly sensitive.
Hyperbolic to Parabolic Relaxation Theory for Quasilinear First Order Systems

Abstract In this paper we study the limiting behavior of nonhomogeneous hyperbolic systems of balance laws when the relaxed equilibria are described by means of systems of parabolic type. In particular we obtain a complete theory for the 2×2 systems of genuinely nonlinear hyperbolic balance laws in 1≳D with a strong dissipative term. A different method, which combines the div–curl lemma with accretive operators, is then applied to study the limiting profiles in the case of nonhomogeneous isentropic gas dynamics. We also investigate relaxation results for some 2≳D cases, which include the Cattaneo model for nonlinear heat conduction and the compressible Euler flow. Moreover, convergence result is also obtained for general semilinear systems in 1≳D.
Estimation of signals containing strongly homogeneous zones

We consider the generic problem of the recovery of signals comprising large strongly homogeneous zones, e.g., locally constant, locally linear, etc., from noisy data given at the output of a linear system. The solution is defined as the minimizer of an objective function combining a data-fidelity term and a regularization term. In our approach, prior knowledge about the presence of large strongly homogeneous zones in the estimate is incorporated directly in the estimator function, through the shape of the regularization term. The latter bears on the differences between consecutive samples. Our main result states that a necessary and sufficient condition that strongly homogeneous zones are recovered in the solution is that the regularization function is nonsmooth for zero-valued differences. In fact, the strongly homogeneous zones involved in such an estimate remain unchanged under small variations of the data. Equivalently, the data space is partitioned into volumes yielding solutions which are strongly homogeneous over the same zones. These theoretical results are illustrated on the deconvolution of a signal. They can be generalized to nonlinear observation systems as well as to the estimation of images.
Numerical study on the shape oscillation of an encapsulated microbubble in ultrasound field

The shape oscillation of an encapsulated microbubble in an ultrasound field is numerically investigated. To predict the nonlinear process, the continuity equation and the Navier–Stokes equation are directly solved by means of a boundary-fitted finite-volume method on an orthogonal curvilinear coordinate system. The mechanics of neo-Hookean membrane is incorporated into the dynamic equilibrium at the bubblesurface. The numerical results show that the membrane raises the natural frequency of an encapsulated bubble especially for small bubble, whereas this effect is attenuated as the initial bubble size grows. For a small encapsulated bubble of which the natural frequency is sufficiently higher than the driving frequency, the oscillation is stable, namely, the oscillatory amplitude is small; besides, the radial mode and shape modes are out of resonance so that no deformation emerges. As the bubble becomes larger, the natural frequencies of encapsulated and gas bubbles get closer, leading to the less apparent difference in oscillatory amplitude between them. Furthermore, shape modes of an encapsulated bubble are prone to be induced when twice of the higher-order natural frequency is approximately equal to the frequency of radial mode particularly when the bubble is at radial resonance for which the large-amplitude pulsation enhances the compressive stress developing in the membrane. In contrast, the shape oscillation is less likely to occur for a gas bubble with micrometer size since the surface tension suppresses the developments of nonspherical shape modes.
Commissioning and performances of the VLT-VIMOS

The Visible Multi-Object Spectrograph VIMOS is a wide field survey instrument in the process of being commissioned for operations at the ESO-VLT. During the first commissioning period, the instrument has confirmed its excellent performances in its three basic modes of operation: direct imaging, multi-slit spectroscopy, and integral field spectroscopy. VIMOS provides the largest imaging field at the VLT with 224 arcmin2. It offers an unprecedented multiplex gain in multi-slit spectroscopy, with on order 800 slits which can be observed simultaneously. The integral field unit has a field up to 54x54 arcsec2, with 6400 spectra recorded at once. The overall efficiency of VIMOS combined to the Melipal unit #3 is confirmed to be as computed on the basis of the measured transmission of optical elements. Image quality is confirmed to be excellent, providing images limited by natural seeing in most conditions. High quality slit masks cut by the laser machine coupled to excellent geometric mask to CCD mapping lead to multi-slit spectra of excellent quality. VIMOS is expected to be offered to the ESO community for reguglar observations in early 2003.
Channel formation in organic field-effect transistors

Results of two-dimensional electrostatic modeling of organic field-effect transistors, focusing on the formation of the conductive channel, are reported. The effect on channel formation of the choice of the source and drain contact metal is investigated for both top- and bottom-contact device structures. High-work-function metal (e.g., gold) source and drain contacts produce a conducting p-type region near these contacts. In contrast, low-work-function metal source and drain contacts (e.g., magnesium) lead to depleted regions. In the center of the device, between the source and drain contacts, the channel carrier density at a fixed gate bias is determined by the work function of the gate contact material, and is essentially independent of the metal used to form the source and drain contacts. The principal difference between top- and bottom-contact structures is the spatial variation of the charge density in the vicinity of the source and drain contacts. The channel carrier density for a fixed gate bias (a.