Miracle-dz/UniFAR-FTUs huggingface dataset:
A nonlinear compensation technique for systems involving hysteresis

This paper presents a simple procedure using a non-linear compensator for eliminating limit cycles in control systems arising due to hysteresis in contactors or due to backlash. The method consists of 1) the insertion of an element of gain Ksgn(z) or K[sgn(z')+1]/2 , and 2) the switching of this element by simple processing of the input and output signals of the original nonlinearity. For a contactor, the technique effectively removes the hysteresis but does not alter the dead zone (which, it is pointed out in one instance, might be an advantage) or, of more importance, the bang-bang characteristic of the element. Furthermore, for the contactors, the compensation technique is found effective irrespective of the waveshape at the nonlinearity input and, therefore, is of some general consequence in design.
Magnetic field-induced noise in directly coupled high Tc superconducting quantum interference device magnetometers

We have measured the noise of several directly coupled high Tc superconducting quantum interference device (SQUID) magnetometers as we change a static magnetic field B while the devices are superconducting. Devices without “flux dams” show an increase in noise at relatively low magnetic fields B∼1 μT. Devices with flux dams can show no deterioration of the noise characteristics for B as large as 34 μT. The flux dams are part of the pickup loop and limit the circulating current Icirc. If Icirc is kept sufficiently low no vortices are forced into the SQUID loop and the noise performance of the magnetometer remains good.
Shelf stability of nanofluids and its effect on thermal conductivity and viscosity

This study proposes a method and apparatus to estimate shelf stability of nanofluids. Nanofluids are fabricated by dispersion of solid nanoparticles in base fluids, and shelf stability is a key issue for many practical applications of these fluids. In this study, shelf stability is evaluated by measuring the weight of settled solid particles on a suspended tray in a colloid versus time and correlated with the performance change of some nanofluid systems. The effects of solid particle concentration and bath sonication time were investigated for selected nanofluids. The results show the applicability of this simple method and the apparatus to evaluate nanofluid shelf stability. Furthermore, it shows that Stokes’ law is not valid for determining the settling time of the tested nanoparticles probably due to their complicated shape and presence of surface modifiers. The effect of shelf stability on thermal conductivity and viscosity was illustrated for some nanofluids. Experimental results show that water-based Al2O3 nanofluids have quite good shelf stability and can be good candidates for industrial applications.
Large wave number vortices in time–periodic flows

The linear stability properties of short wavelength vortices within time–periodic flows are examined using a WKB–based asymptotic analysis. Such vortices typically have an instantaneous growth rate considerably larger than the time–scale of the underlying flow and thus have often been studied using quasi–steady techniques. A major drawback of these quasi–steady approaches is that although they are able to determine the instantaneous flow structure they are of no use in describing the evolution of the modes. It is shown how rational asymptotic analysis based on WKB ideas overcomes this deficiency and enables the form of the neutral stability curve to be obtained for short wavelengths. The technique is applied to three problems. First, the key features of the analysis are exemplified by careful consideration of a model problem which is motivated by the physical situation of the sinusoidal heating of a horizontal flat plate bounding a semi–infinite layer of fluid. The governing linearized stability equations take the form of a system which is sixth order in the spatial variable and second order in time; however, the important features of this system are captured by our model which is only second order in the spatial coordinate and first order in time. The second physically important flow examined is the motion induced in a viscous fluid surrounding a long torsionally oscillating cylinder (a curved Stokes flow). Detailed asymptotic and numerical studies of both the model and the two physically motivated flows are undertaken and it is shown how the analytical results provide good qualitative agreement with the numerical findings at quite modest wavenumbers. The methodology adopted here may be used as a basis for the rational study of the stability properties of other time–periodic flows. A key result forthcoming from this study is the demonstration that the first few terms in the relevant high wavenumber form of the neutral curve for modes in an oscillatory flow may be derived relatively quickly with minimal computational effort.
On Plug-in Rules for Local Smoothing of Density Estimators

Optimal local smoothing of a curve estimator requires knowledge of various derivatives of the curve in the neighbourhood of the point at which estimation is being conducted. One empirical approach to selecting the amount of smoothing is to employ pilot estimators to approximate those derivatives, and substitute the approximate values into an analytical formula for the desired local bandwidth. In the present paper we study how bandwidth choice for the pilot estimators affects the performance of the final estimator. Our conclusions are rather curious. Depending on circumstance, the pilot estimators should be substantially oversmoothed or undersmoothed, relative to the amount of smoothing that would be optimal if they were to be employed themselves for point estimation. Occasionally, the optimal amount of undersmoothing is so extreme as to render the pilot estimators inconsistent. Here, the resulting local bandwidth is asymptotically random; it is not asymptotic to a sequence of constants.
Unbiased Estimating Equations From Working Correlation Models for Irregularly Timed Repeated Measures

The method of generalized estimating equations (GEEs) has been criticized recently for a failure to protect against misspecification of working correlation models, which in some cases leads to loss of efficiency or infeasibility of solutions. However, the feasibility and efficiency of GEE methods can be enhanced considerably by using flexible families of working correlation models. We propose two ways of constructing unbiased estimating equations from general correlation models for irregularly timed repeated measures to supplement and enhance GEE. The supplementary estimating equations are obtained by differentiation of the Cholesky decomposition of the working correlation, or as score equations for decoupled Gaussian pseudolikelihood. The estimating equations are solved with computational effort equivalent to that required for a first-order GEE. Full details and analytic expressions are developed for a generalized Markovian model that was evaluated through simulation. Large-sample “sandwich” standard errors for working correlation parameter estimates are derived and shown to have good performance. The proposed estimating functions are further illustrated in an analysis of repeated measures of pulmonary function in children.
Host Galaxies and Circumgalactic Environment of “Narrow Line” Seyfert 1 Nuclei

This paper presents a statistical study of the host galaxies and environment for a sample of 27 "narrow line" Seyfert 1 (NLSy1) nuclei, based on a computer-aided search of companions in the Digitized Sky Survey. The sample includes all objects listed as NLSy1 in the Véron-Cetty & Véron catalog (8th edition) with redshift in the range 0.010 ≤ z ≤ 0.061 and Galactic latitude |b| ≥ 30°. We compared the environments of NLSy1's with those of Seyfert 1 and Seyfert 2 galaxies using the method and the Seyfert samples employed in 1999 by Dultzin-Hacyan et al. The frequency of "physical" companions was measured within a search radius equal to 3 times the diameter DS of each NLSy1 and up to a projected linear distance of ≈100 kpc. No statistical difference was found between the environments of NLSy1's and those of Seyfert 1 galaxies. Our results further suggest that NLSy1 hosts may show fewer companions and may be preferentially farther away from bright companion galaxies than normal galaxies with similar morphological type, diameter, and redshift distribution. The results for host galaxies and environments help to disprove the hypothesis that NLSy1 objects have characteristics similar to those of Seyfert 2 galaxies: whereas Seyfert 2 galaxies show a highly significant excess of bright companions, Seyfert 1's and NLSy1's do not. The morphological distribution of NLSy1's and Seyfert 1 objects is similar, but NLSy1 nuclei are hosted in galaxies smaller than Seyfert 1 and nonactive galaxies, to a statistical confidence level of 95%. These results support the interpretation of NLSy1 nuclei (suggested by X-ray observations) as Seyfert 1 nuclei with higher Eddington ratio, since smaller diameter galaxies may host central black holes of lower mass.
Automatic threshold selection using the wavelet transform

Abstract A new method of peak analysis for threshold selection is presented. It is based on the wavelet transform which provides a multiscale analysis of the information content of the histogram of an image. We show that the detection of the zero-crossings and the local extrema of a wavelet transform of the histogram gives a complete characterization of the peaks in the histogram, that is to say, the values at which they start, end, and are extreme. These values are used for the unsupervised and automatic selection of a sequence of thresholds describing a coarse-to-fine analysis of histogram variation. The results of using the proposed technique are presented in the case of different images.
Some optimality properties of FDR controlling rules under sparsity

False Discovery Rate (FDR) and the Bayes risk are two different statistical measures, which can be used to evaluate and compare multiple testing procedures. Recent results show that under sparsity FDR controlling procedures, like the popular Benjamini-Hochberg (BH) procedure, perform also very well in terms of the Bayes risk. In particular asymptotic Bayes optimality under sparsity (ABOS) of BH was shown previously for location and scale models based on log-concave densities. This article extends previous work to a substantially larger set of distributions of effect sizes under the alternative, where the alternative distribution of true signals does not change with the number of tests m, while the sample size n slowly increases. ABOS of BH and the corresponding step-down procedure based on FDR levels proportional to n−1/2 are proved. A simulation study shows that these asymptotic results are relevant already for relatively small values of m and n. Apart from showing asymptotic optimality of BH, our results on the optimal FDR level provide a natural extension of the well known results on the significance levels of Bayesian tests.
ESTIMATION OF MULTIVARIATE SHANNON ENTROPY USING MOMENTS

Three new entropy estimators of multivariate distributions are introduced. The two cases considered here concern when the distribution is supported by a unit sphere and by a unit cube. In the former case, the consistency and the upper bound of the absolute error for the proposed entropy estimator are established. In the latter one, under the assumption that only the moments of the underlying distribution are available, a non‐traditional estimator of the entropy is suggested. We also study the practical performances of the constructed estimators through simulation studies and compare the estimators based on the moment‐recovered approaches with their counterparts derived by using the histogram and kth nearest neighbour constructions. In addition, one worked example is briefly discussed.
The measured point response functions for the CERES Flight Model 5 instrument

The Clouds and Earth Radiant Energy System (CERES) Flight Model 5 (FM5) instrument is scheduled to be launched this year aboard the NPP spacecraft in order to continue the Climate Data Record for Earth radiation budget. CERES data will be used together with measurements from the Visible Infra-red Imager Radiometer Suite (VIIRS) to compute cloud information for each CERES pixel. Knowledge of the point response function (PRF) of CERES is essential to accurately align these data sets. The Radiation Calibration Facility at Northrop Grumman includes the PRF Source, an optical devise for measuring the PRF. This paper presents the analysis of these tests and the resulting PRF for each of the three channels.
Realistic models for evolving globular clusters: core collapse with a mass spectrum

L'evolution des amas globulaires est modelisee, apres l'effondrement du centre, par integration directe de l'equation de Fokker-Planck multi-masse. Ce modele inclut un spectre de masse realiste d'etoiles de masses comprises entre 0.1 et 1.2 M ○. et les effets de chauffage dus a la formation de binaires par un processus de trois corps et a leurs durcissements posterieurs. L'evolution de la densite et de la temperature centrales, les effets de la fonction de masse, la dependance des oscillations sur les parametres de l'amas et les profils radiaux sont analyses.
CONTINUOUS HYBRID BLOCK STOMER COWELL METHODS FOR SOLUTIONS OF SECOND ORDER ORDINARY DIFFERENTIAL EQUATIONS

In this paper, we present continuous hybrid stomer cowell methods. Using the method of collocation and interpolation of power series approximate solution to derive a continuous linear multistep method. Block method was later used to generate the non overlapping solutions at selected grid points. The method developed, is consistent, zero-stable and convergent. The performance of the new block method was tested with some second order initial value problems and it was found to compare favourably with the existing methods.
DYNAMIC ANALYSIS OF THE FLEXIBLE ROD OF QUICK-RETURN MECHANISM WITH TIME-DEPENDENT COEFFICIENTS BY THE FINITE ELEMENT METHOD

Abstract The transient amplitude, dynamic stability and steady-state response of a flexible rod of a high-speed quick-return mechanism are investigated in this paper. The crank drives the rod by means of a translating/rotating joint at a constant speed. The flexible rod is divided into two regions. Each region has a time-dependent length and is modelled by the Timoshenko and Euler beam theories. A special finite element method with time-dependent shape and Hamilton's principle is employed to derive the governing equation, which has time-varying coefficients. By using the Runge–Kutta numerical method, the transient amplitudes are obtained. The steady-state responses due to harmonic excitation are determined by the harmonic balance method. Subsequently, Bolotin's method is used to solve Mathieu–Hill's type equation for the dynamic stability analysis. The stable–unstable boundaries are obtained from the condition that the set of linear homogeneous equations should have a non-trivial solution.
Adaptive fuzzy output feedback backstepping control of pure‐feedback nonlinear systems via dynamic surface control technique

In this paper, an adaptive fuzzy backstepping dynamic surface control approach is considered for a class of uncertain pure‐feedback nonlinear systems with immeasurable states. Fuzzy logic systems are first employed to approximate the unknown nonlinear functions, and then an adaptive fuzzy state observer is designed to estimate the immeasurable states. By the combination of the adaptive backstepping design with a dynamic surface control technique, an adaptive fuzzy output feedback backstepping control approach is developed. It is proven that all the signals of the resulting closed‐loop system are semi‐globally uniformly ultimately bounded, and the observer and tracking errors converge to a small neighborhood of the origin by choosing the design parameters appropriately. Simulation examples are provided to show the effectiveness of the proposed approach. Copyright © 2012 John Wiley & Sons, Ltd.
Lévy flight applied to random media problems

A random-medium model being the correlated distribution of points positioned in E-dimensional Euclidean space is considered. The construction of the medium starts from noncorrelated (Poisson) uniform distribution of parent particles; each of them initiates the finite Marcov chain of its descendants. The complete collection of correlation functions of all orders within the scope of the model has been obtained. The use of three-dimensional stable laws (Levy laws) as transition probability density allows one to express the correlation functions of all orders in terms of two point ones only. Some numerical results are presented and discussed in connection with fractal structure simulation.
Quality of Piano Tones

A synthesizer was constructed to produce simultaneously 100 pure tones with means for controlling the intensity and frequency of each one of them. The piano tones were analyzed by conventional apparatus and methods and the analysis set into the synthesizer. The analysis was considered correct only when a jury of eight listeners could not tell which were real and which were synthetic tones. Various kinds of synthetic tones were presented to the jury for comparison with real tones. A number of these were judged to have better quality than the real tones. According to these tests synthesized piano like tones were produced when the attack time was less than 0.01 sec. The decay can be as long as 20 sec for the lower notes and be less than 1 sec for the very high ones. The best quality is produced when the partials decrease in level at the rate of 2 db per 100 cps increase in the frequency of the partial. The partials below middle C must be inharmonic in frequency to be piano like.
Coupled Partial Differential Equations Method for InSAS Interferogram Filtering

In this paper, a coupled nonlinear diffusion partial differential equations (PDE) method for Interferometric Synthetic Aperture Sonar(InSAS) interferogram filtering was introduced. Many previous PDE methods in this area usually use Gauss pre-filtering. The choice of variance in Gauss function plays a very important role in the quality of the image obtained. Manually choice of the variance can hardly reach the self-adaptation aim. Using nonlinear diffusion equation to instead Gauss pre-filtering can overcome the disadvantage mentioned above. Numerical experiment results indicate that this coupled PDE method is able to effectively reduce the noise and preserve edge information. And it is important for InSAS real time processing.
Surface Waves on Two‐Dimensional Corrugated Structures

The characteristic equation is derived for the propagation of surface waves guided by a planar two-dimensional corrugated structure. This equation is solved numerically to obtain the propagation wave number as a function of the direction of propagation on the surface. The data obtained illustrate the anisotropic nature of the wave propagation. In addition, an isolated surface wave is found to exist with its propagation wave number in a ‘forbidden’ region of wave number space. The relevance of this wave to a transmission null in a phased array antenna is discussed.
Continuous and quad-graph integrable models with a boundary: Reflection maps and 3D-boundary consistency

This thesis is focusing on boundary problems for various classical integrable schemes. First, we consider the vector nonlinear Schrodinger (NLS) equation on the halfline. Using a Backlund transformation method which explores the folding symmetry of the system, classes of integrable boundary conditions (BCs) are derived. These BCs coincide with the linearizable BCs obtained using the unified transform method developed by Fokas. The notion of integrability is argued by constructing an explicit generating function for conserved quantities. Then, by adapting a mirror image technique, an inverse scattering method with an integrable boundary is constructed in order to obtain N-soliton solutions on the half-line, i.e. N-soliton reflections. An interesting phenomenon of transmission between different components of vector solitons before and after interacting with the boundary is demonstrated. Next, in light of the fact that the soliton-soliton interactions give rise to Yang-Baxter maps, we realize that the soliton-boundary interactions that are extracted from the N-soliton reflections can be translated into maps satisfying the set-theoretical counterpart of the quantum reflection equation. Solutions of the set-theoretical reflection equation are referred to as reflection maps. Both the Yang-Baxter maps and the reflection maps guarantee the factorization of the soliton-soliton and soliton-boundary interactions for vector NLS solitons on the half-line. Indeed, reflection maps represent a novel mathematical structure. Basic notions such as parametric reflection maps, their graphic representations and transfer maps are also introduced. As a natural extension, this object is studied in the context of quadrirational Yang-Baxter maps, and a classification of quadrirational reflection maps is obtained. Finally, boundaries are added to discrete integrable systems on quad-graphs. Triangle configurations are used to discretize quad-graphs with boundaries. Relations involving vertices of the triangles give rise to boundary equations that are used to described BCs. We introduce the notion of integrable BCs by giving a three-dimensional boundary consistency as a criterion for integrability. By exploring the correspondence between the quadrirational Yang-Baxter maps and the so-called ABS classification, we also show that quadrirational reflection maps can be used as a systematic tool to generate integrable boundary equations for the equations from the ABS classification.
Necklace solid-on-solid models of interfaces and surfaces

Using the exact generating functions for solid-on-solid models, the authors construct 'necklace' partition functions for wetting and prewetting at a sticky wall in two (bulk) dimensions. Three-component generalisations of these models, constructed to study interfacial wetting, are introduced and solved. Based on these models they discuss the types of interfacial critical behaviour to be expected in three-component systems in two dimensions.
Barrier heights between ground states in a model of RNA secondary structure

Secondary structure formation is an important factor influencing the behaviour of many types of naturally occurring RNA molecules. RNA secondary structure also provides an example of a disordered system showing frustration and a rugged energy landscape with many alternative ground states. We use a numerical method to estimate energy barrier heights between a set of alternative ground-state structures of a given sequence. Both the mean barrier height and the maximum barrier height for a given sequence scale with a sequence length N approximately as . The matrix h of barriers is exactly ultrametric, which means that structures form an exactly hierarchical set of clusters based on barrier heights. The matrix of distances d between structures is correlated with h, but with large fluctuations. Hence, the d matrix is approximately ultrametric, but the clustering of structures based on distances is not perfectly hierarchical. Certain base pairs are observed to be present in every ground-state structure. These `frozen' pairs divide the molecule up into mutually inaccessible pieces. All of the separate pieces contribute to determining the distance between structures, but only the largest piece will contribute to the barrier height. The length of the largest piece varies between sequences, and scales in proportion to N on average. We compare these results with studies of other disordered systems, and discuss the consequences for the folding of naturally occurring RNAs.