Miracle-dz/UniFAR-FTUs huggingface dataset:
Aspects of the equilibrium puff in transitional pipe flow

Flow-visualization studies in transitional pipe flow are used to reveal the mechanism responsible for the self-sustenance of a turbulent equilibrium puff. The upstream laminar fluid continuously enters the relatively-slower-moving turbulent puff around the pipe centre. The passage of this high-speed laminar plug flow past the slower fluid that resides near the wall at the upstream interface leads to the shedding of a train of three-dimensional wake-like vortices near the wall. A helical motion near the upstream interface is associated with the vortex-shedding process. The remainder of the puff is a cone of turbulence filled with these wake-like vortices that are decaying slowly; the prominent feature of the decay region is the longitudinal vortices that are apparently undergoing stretching. No toroidal vortex has been observed in the instantaneous flow field at the upstream interface of an individual puff. On the other hand, the wake-like vortices reported here have not been observed before because their three-dimensional and random nature does not allow detection by an ensemble-averaging that is not phase-referenced appropriately.
On the distribution of frequency ratios of kHz quasi-periodic oscillations

The width (�ν), root mean squared amplitude (rS) of lower and upper kHz quasi-periodic oscillations (QPOs) from accreting neutron stars vary with frequency. Similarly, the QPO frequency varies with the source count rate (S). Hence, the significance of a QPO, scaling as S × r 2 / p �ν will also depend on frequency. In addition, the significance also scales up with the square root of the integration time of the Fourier power density spectrum (T ). In practice and in most analysis, T is constrained (e.g. limited by the RXTE orbital period if th e source is occulted by the earth) or minimized to increase the number of detections. Consequently, depending on the way data are considered, kHz QPOs (the lower, the upper or both kHz QPOs) may be detected only over a limited range of their frequency spans or detected predominantly at some frequencies, leading potentially to biases in the observed distributions of frequencies or frequency ratios. Although subject of much controversy, an observed clustering of QPO frequency ratios around 3/2 in Sco X-1, also seen in other sources, has been previously used as an argument supporting resonance based models of neutron star QPOs. In this paper, we measure how the statistical significance of both kHz QPOs vary with frequency. For this purpose, we consider three prototype neutron star kHz QPO sources, namely 4U1636-536, 4U0614+091 and Sco X-1, whose QPO parameters have different, though representative, dependence with frequency. As the significanc e of QPO detection depends on frequency, we show that in sensitivity-limited observatio ns (as in the case of the RXTE/PCA), a simultaneous detection of both the lower and upper kHz QPOs can only be achieved over limited frequency ranges. As a result, even a uniform distribution of QPO frequencies will lead to peaks (in particular around 3/2) in the histogram of r atios of simultaneous kHz QPO frequencies. This implies that the observed clustering of r atios of twin QPO frequencies does not provide any evidence for intrinsically preferred frequ ency ratios in those systems, thus weakening the case for a resonance mechanism at the origin of neutron star kHz QPOs.
Oxidation induced stacking faults in n‐ and p‐type (100) silicon

The formation of stacking faults during thermal oxidation of silicon has been investigated. The length and the density of stacking faults, in both n‐ and p‐type 5‐cm‐diam (100) silicon wafers obtained from various manufacturers, were determined as a function of time and temperature of oxidation in dry and steam ambients. There appeared to be two categories of stacking faults. In the first category, the length of the stacking fault was given by L= (const) tn exp(−Q/kT), where n and Q are, respectively, 0.85 and 2.55 eV for dry oxidation and 0.66 and 2.37 eV for steam oxidation. This length was independent of the type (p or n) of the wafer. In the second category, the length of the stacking faults varied randomly across the wafer surface. The number of such faults was only about 5% of the total. For a given oxidation condition, the density of the stacking faults was an order of magnitude or more higher in n‐type wafers than that in p‐type wafers. Except for the very short periods of oxidation (<20 min) the .
Homological stability for unlinked Euclidean circles in $R^3$

We prove a homological stability theorem for unlinked Euclidean circles in $R^3$ and use a theorem of Hatcher and Brendle to deduce homological stability for unlinked embedded circles. We discuss generalizations to unlinked Euclidean spheres with additional structure and applications to homological stability for various groups of diffeomorphisms of connected sums of $D^2 \times S^1$.
A quarter century of gyrotron research and development

The development of small-orbit gyrotrons operating at voltages /spl les/100 kV is reviewed. Gyrotron oscillators have been developed to produce unprecedented 200-kW average power levels at frequencies spanning the range of 28-140 GHz with current work aimed at achieving 1-MW average power. They are widely used in plasma-heating studies and are the natural choice for material processing in the millimeter-wave region. Gyrotron amplifiers have exceeded the peak power limits of more conventional amplifiers at both 35 and 94 GHz, and have been used in a few radars. Gyro-amplifiers under development have been designed to surpass both the peak power and the average power limits of conventional amplifiers, and are anticipated to be widely accepted in millimeter-wave radar systems. Gyrotron amplifiers operating at voltages /spl sim/0.5 MV that are being evaluated for accelerator applications were reviewed in this journal in 1996 and are not included in this review paper,.
Average treatment effect estimators – inefficiency – minimisation of variance

In this paper, we show the inability of a recent average treatment effect estimator (ATE) to catch up the asymptotic semiparametric efficiency bound of Hahn (1998) although it minimises the mean squared error. Additionally, we propose the use of a minimum variance unbiased uniformly estimator of the propensity score in order to minimise the loss of efficiency.
Online cursive script recognition using local affine transformation

The problem of extraction, description, and estimation of handwriting deformation in online character recognition is discussed. First, feature-point correspondence is extracted between an input pattern and a reference pattern by elastic matching and a deformation vector field (DVF) is generated. Second, the DVF is expanded into an infinite series by applying iterative local affine transformations. Finally, the interpattern distance is calculated between the input pattern and the reference pattern superposed by low-order components of local affine transformations. Recognition tests made on cursive kanji character data have revealed the high discrimination ability of this method. <<ETX>>
Cluster Reduction : Deletion or Coalescence?

I show that a consequence of Correspondence Theory in Optimality Theory is that, for processes such as cluster reduction, if MAX outranks UNIFORMITY, candidates displaying coalescence are preferred to those displaying true deletion. It is thus incumbent on the analyst to identify the constraints that select appropriate coalescence candidates, even for apparent deletion cases. I show how Lamontagne and Rice’s (1995) account of the D-effect in Navajo must be modified to ensure the correct outcome in a language where both coalescence and apparent deletion are repairs to cluster constraint violations. If, for other reasons, it is necessary that UNIFORMITY outrank MAX, the admission of MAX(Feature) constraints becomes unavoidable. An analysis of certain cluster reduction phenomena in Ibiza Catalan shows how complex coda constraints, perceptual markedness constraints for clusters, Paradigm Uniformity, and featural faithfulness interact to derive a pattern of contextual variation. The paper includes a review of Correspondence Theory focusing on its effects in cluster reduction.
On Expanded and Improved Affinity Propagation Clustering Algorithm

Facing to the shortcoming of Affinity Propagation algorithm (AP), we present two expanded and improved AP algorithms. In the two algorithms, the AP algorithm based on Grid Cell (APGC) is an effective extension of AP algorithm on the level of grid cells, and the AP clustering algorithm based on Near neighbour Sampling (APNS) is trying to make some improving in time and space complexity. From some simulated comparison experiments of three algorithms, we know that APGC and APNS algorithms have evident improving than AP algorithm in time and space complexity. They can not only get a good clustering quality for massive data sets, but also filtrate noises and isolates well. So we can say they are two effective clustering algorithms with much applied prospect. At last, several research directions are presented.
The stability of nonlinear dissipative systems

This short paper presents a technique for generating Lyapunov functions for a broad class of nonlinear systems represented by state equations. The system, for which a Lyapunov function is required, is assumed to have a property called dissipativeness. Roughly speaking, this means that the system absorbs more energy from the external world than it supplies. Different types of dissipativeness can be considered depending on how one chooses to define "power input. " Dissipativeness is shown to be characterized by the existence of a computable function which can be interpreted as the "stored energy" of the system. Under certain conditions, this energy function is a Lyapunov function which establishes stability, and in some cases asymptotic stability, of the isolated system.
Validation Study of a Multidomain Spectral Code for Simulation of Turbulent Flows

A Chebyshev multidomain staggered-grid method (CMSM) presented by Kopriva for numerical simulation of three-dimensional compressible turbulent flows, is validated. Computations with the CMSM of an isotropic turbulence and a fully developed turbulent channel flow are compared with previously published results. Turbulence initiation of the isotropic turbulence on the Chebyshev grid is discussed. Low-resolution simulations ensure transition of an initial laminar channel flow to a turbulent channel flow. The turbulent kinetic energy spectrum has sufficient dropoff (indicating a resolved solution) at a minimum of 3 to 6 points per wave number for a polynomial approximation of 13 to 10, respectively
THE ABDUS SALAM INTERNATIONAL CENTRE FOR THEORETICAL PHYSICS A STATISTICAL ANALYSIS OF RADIO PULSAR TIMING NOISE

We present an analysis of the timing observations on 27 radio pulsars, collected at Hartebeesthoek Radio Astronomy Observatory (HartRAO), which span between ∼ 9 and 14 yrs. Our results show that the observed frequency second derivative (ν̈obs) are highly non-stationary, with magnitude and sign depending randomly on time and data span length. Statistical analysis of a complete sample of 391 (25 HartRAO and 366 Jodrell Bank Observatory) pulsars reveals no significant correlation between ν̈obs and both the pulsar spin-down rate (Ṗ) and the characteristic age (τc). Irrespective of sign, we find ∼ 0.20 and −0.30 as the correlation coefficients between the measured braking indices and, respectively, Ṗ and τc. This result reaffirms an earlier conclusion by Chukwude (2003) that the braking indices of most radio pulsars, obtained through the standard timing technique, are strongly dominated by sustained random fluctuations in the observed pulse phase.
Phased array pulse Doppler tomography

A major problem in ultrasound Doppler has been the lack of quantitation of the complete vectorial velocity distribution in a cross-sectional plane. The authors derive general formulae for the magnitude of the velocity and its direction relative to a known coordinate system using velocity components measured from two beam directions. In order to improve the imaging quality, two methods combining more than two conventional color flow images appropriately are developed. One method is based on weighted averaging of vectorial velocity fields computed from pairs of color flow images. The other method employs the least squares approach, attempting to increase the signal-to-noise ratio. Some results of imaging experiments with both artificial objects and clinical data are presented. <<ETX>>
Leader-Based Consensus of Heterogeneous Nonlinear Multiagent Systems

This paper considers the leader-based consensus of heterogeneous multiple agents with nonlinear uncertain systems. Based on the information obtained from the following agents’ neighbors, leader observers are designed by the following agents to estimate the leader’s states and nonlinear dynamics. Then, to achieve leader-based consensus, adaptive distributed controllers are designed for the following agents to track the designed corresponding leader observers. The effectiveness of the leader observers and distributed consensus controllers are illustrated by formal proof and simulation results.
A triple decomposition of the fluctuating motion below laboratory wind water waves

Understanding of the dynamics of the top meters of the ocean requires an improvement of present knowledge about interactions between wind waves, mean sheared current, and turbulence. To achieve this goal, a key point lies in relevant definitions and evaluations of orbital and turbulent motions. The aim of this paper is to build and validate a separation technique allowing one to distinguish all three crucial contributions of the fluctuating motion, namely the potential and rotational parts of the orbital motion, as well as turbulent fluctuations. The whole method is first developed and tested for periodic rotational waves. The first step of this technique consists of a determination of the instantaneous stream function associated with the potential motion induced by the waves in presence of a linear sheared current. The second step consists of a linear filtration of the remaining motion from which the orbital rotational motion is extracted. The strong hypotheses involved in the technique are then carefully checked and shown to be relevant in the case of laboratory wind waves. The method is finally applied to experimental data obtained by laser Doppler velocimetry measurements in a wind-water laboratory facility. Influence of the mean sheared current on the prediction of orbital velocities is pointed out, and the orbital rotational contribution is found to have a significant magnitude.
A frequency condensation method for the eigenvalue problem

SUMMARYA frequency condensation method is presented for solving the eigenvalue problem of a large matrix system.The eigenproblem is reduced to a smaller problem by condensing the sti•ness and mass matrices. As distinctfrom the Guyan method, the frequency condensation method is based on approximation preserving eigen-values in a preset frequency range and e•ective procedure of master and slave selection. A numericalexample and comparison with subspace iteration and Lanczos methods demonstrate good accuracy and thehigh performance of this method. #1998 John Wiley & Sons, Ltd. Commun. Numer. Meth. Engng, 14, 1–8 (1998) KEY WORDS frequency condensation method; large matrix systems; Guyan method INTRODUCTIONResearch into modern problems of dynamics and strength of a complex structure, with the helpof a ﬁnite element method, leads to mathematical models, which are described by large matrixequations. The solution of these equations is frequently transformed to a large eigenvalueproblem. It is known that this eigensolution for small matrices is practically a closed problem.However, for large matrices it is far from atrivial problem and the choice of an optimum methodof eigensolution is not simple.At present, it is possible to distinguish between two main directions of the eigensolution forlarge matrix systems: iterative methods and condensation methods.The most e•ective among iterative methods are the subspace iteration and Lanczos methods.The subspace iteration method is atechniquewhich determines onlythe lowesteigenvalues of thematrix system.
Optimal layout of fringe projection for three-dimensional measurements

We optimize the layout of each light plane in a dual-view multistripe measurement system by employing spatial geometry analysis to avoid ambiguity. The imaging regions of every light plane can be labeled uniquely on two image planes within a certain measurement depth. More- over, the flexible density of fringe patterns corresponding to the different measurement depths is immediately projected without the conventional coding procedure. Some experi- ments verify the effectiveness of the proposed method ap- plied in high-resolution 3-D measurements. © 2008 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2931577
The local approximate output regulation problem: convergence region estimates

In this paper, the problem of local approximate output regulation is considered. The presented results answer the question: given a controller solving the local approximate output regulation problem, how to estimate the set of initial conditions for which approximate output regulation occurs. The results are illustrated by a disturbance rejection problem for the TORA system. Copyright © 2004 John Wiley & Sons, Ltd.
Near optimal blind deconvolution

A solution is proposed for blind deconvolution problems, i.e. the estimation of the impulse response of an unknown discrete-time channel given the output data sequence and statistical information on the input sequence. The solution approaches the optimal one when the input sequence is independent and identically distributed and the channel distortion is small. Numerical results are given in the case of the optimal nonlinear function, which depends on the input probability density function, and in the case of the very simple sign function. The technique can be used iteratively if the distortion is not small. <<ETX>>
Assimilation of Equatorial Waves by Line-of-Sight Wind Observations

This paper investigates the potential of line-of-sight (LOS) wind information from a spaceborne Doppler wind lidar to reduce uncertainties in the analysis fields of equatorial waves. The benefit of LOS winds is assessed by comparing their impact to that of a single wind component, full wind field information, and mass field data in three- and four-dimensional variational data assimilation. The dynamical framework consists of nonlinear shallow-water equations solved in spectral space and a background error term based on eigenmodes derived from linear equatorial wave theory. Based on observational evidence, simulated wave motion fields contain equatorial Kelvin, Rossby, mixed Rossby‐gravity, and the lowest two modes of the westward-propagating inertio‐gravity waves. The same dynamical structures are included, entirely or partially, into the background error covariance matrix for the multivariate analysis. The relative usefulness of LOS data is evaluated by carrying out ‘‘identical twin’’ observing system simulation experiments and assuming a perfect model. Results from the experiments involving a single observation or an imperfect background error covariance matrix illustrate that the assimilation increments due to LOS wind information rely more on the background error term specification than the full wind field information. This sensitivity is furthermore transferred to the balanced height field increments. However, all assimilation experiments suggest that LOS wind observations have a capability of being valuable and need supplemental information to the existing satellite mass field measurements in the Tropics. Although the new wind information is incomplete, it has a potential to provide reliable analysis of tropical wave motions when it is used together with the height data.
Exergetic analysis of a long two-phase closed thermosyphon system

The focus of present study is to provide a simplified engineering model of the long thermosyphon. In this paper, combination of the thermal network analysis and the lumped capacity were used in order to simulate thermal characteristics of a long two-phase closed thermosyphon operation. Then the T-s diagram of the thermosyphon processes was presented based on the combination model analysing results. Finally, the exergy analysis of the thermosyphon components was performed for different refrigerants as the working fluids. The results show that increasing the ambient heat transfer coefficient causes to decrease of the condenser and total exergy destruction rates.
A Predictor-Variable Selection Program

This package contains programs to perform the following standard types of regression analyses: (a) full regression, (b) forward selection, and (c) backward elimination. The special feature of the package is a program for determining the optimum relative test lengths so as to maximize the multiple correlation for a fixed total testing time using the algorithm developed by Woodbury and Novick (1967).
On the Weil-Siegel formula.

The Weil-Siegel formula identifies the integral of a certain theta function s a value of an Eisenstein series. A very general Version of such a formula was proved by Weil [23] under a certain condition which implied the convergence of the integral of the theta function and the absolute convergence of the Eisenstein series at the point in question. In the present paper we will prove that the Weil-Siegel formula for even dimensional anisotropic quadratic forms over a number field is valid with no restrictions. Of course, for such forms, the integral of the theta function is always absolutely convergent; but in general, the point at which the Eisenstein series must be evaluated may lie outside the r nge of absolute convergence of that series. Thus we must study the analytic continuation of the Eisenstein series and its behavior in the critical strip. We now give a more precise description of our result and an outline of the proof.
Seuillage d'images base sur l'operateur de Teager-Kaiser

Histogram image thresholding is a classical segmentation process. This work deals with bilevel thresholding in order to extract useful binary information. A new thresholding method which incorporates the pixel contextual's information is presented. This method uses image edges to estimate the threshold value. More precisely, instead of using an edge dectector, the Teager-Kaiser Energy Operator (TKEO) is used to estimate the pixel's activity. Indeed, this operator reflects much more the pixel energy activity compared to classical edge detectors (Laplacian,.). The thresholding results obtained on synthetic and reals data, show the need of including contextual image information. Comparisons with Otsu and Kitler methods, show that the TKEO is able to estimate threshold values of practical interest.
Improving the Accuracy of Phylogenetic Estimation by Combining Different Methods

Three methods of phylogenetic tree estimation, UPGMA clustering (UP), maximum parsimony (MP), and neighbor joining (NJ), were used to estimate trees from a large simulation study of 5,400 eight-taxon data sets. The data sets represented nine evolutionary models and 20 tree topologies. The agreement of the trees estimated by the three methods was highly correlated (0.71) with the average agreement with the true tree from which the data sets had been generated. A simple index is proposed for the agreement of different estimation methods that can serve as a measure of the reliability of the joint estimate. This index was coupled with an unbiased character weighting procedure to increase the accuracy of estimation. Accuracy was increased by an average of 24% by use of this procedure in 47 of 61 data sets examined