Miracle-dz/UniFAR-FTUs huggingface dataset:
Contraction theory-based recursive design of stabilising controller for a class of non-linear systems

The study addresses stabilisation problem of a class of non-linear systems using contraction principle. For this purpose, contraction-based systematic design of control function is presented. Generally, Lyapunov stability-based backstepping technique is widely used to design controllers for strict feedback class of non-linear systems in a recursive manner. However, the present study highlights the usage of contraction-based concepts for stability analysis and presents a systematic procedure to select a single controller for stabilisation of systems having dynamics in strict feedback form. The approach establishes exponential stability of system states. The procedure helps in identifying coordinate transformation to establish contracting nature of the given system. Design of output tracking controller for single-link manipulator system with actuator dynamics is considered to highlight the procedure. The proposed methodology is extended to address synchronisation problem of non-linear systems. As a particular case, synchronisation problem of chaotic systems belonging to the addressed class of systems is explored. Systems to be synchronised are assumed to be connected in a chain through one way coupling. The general scalar coupling function is obtained by utilising the proposed algorithm and stability results are established using partial contraction theory. Numerical simulations are presented at appropriate places to verify the efficacy of the proposed approach.
New mixed formulations for problems in elasticity

Classical mixed formulations of the boundary‐value problem of linear elasticity are reviewed, and a new three‐field formulation is introduced. The formulation is an extension of the classical Hu‐Washizu approach, and takes the form of a non‐standard mixed problem. Convergence of finite element approximations of both the old and new methods are discussed, with an emphasis on their behaviour in the incompressible limit. Conditions for the stability and uniform convergence of the new method are presented, and it is shown that the Pian‐Sumihara basis, when used in the new formulation, leads to a convergent method.
Sedimentation of agglomerated nanoparticles under cell culture conditions studied by image based analysis

Toxic effects of nanoparticles can be analyzed with alveolar macrophages in vitro. To quantify exposure of cells to particles we analyzed the sedimentation of nanoparticle agglomerates in cell culture medium (MEM) by means of phase contrast microscopy. Particles were suspended by brief ultrasonication in MEM and pipetted into a glass bottom culture dish on the stage of a Nikon-Biostation under cell culture condition. Successive images were captured from the lowermost optical plane and were converted into binary images. The number of agglomerates (N) as well as the particle-covered area (A) were determined by image analyses. Typically, N increased to a maximum value before it partially decayed due to overlapping and/or optical interference of particles, and finally became constant. In contrast, A increased in a monophasic manner. By means of mathematical modeling we identified the endpoint of sedimentation of particle agglomerates, which is an important though a largely neglected event in most cell culture experiments. This endpoint could be calculated from an approximated model function. As the method can be employed in the presence of cells, a parallel evaluation of particle sedimentation and particle uptake appears possible.
Active wall motions for skin-friction drag reduction

In the present study we investigate a possibility of reducing skin-friction drag in a turbulent channel flow with active wall motions. The wall is locally deformed according to two successful control strategies [J. Fluid Mech. 262, 75 (1994); J. Fluid Mech. 358, 245 (1998)]. Results show that overall 13–17% drag reductions are obtained with the active wall motions, and turbulence intensities and near-wall streamwise vortices are significantly weakened. It is remarkable that instantaneous wall shapes are elongated in the streamwise direction and resemble riblets in appearance. However, the mechanism of the present drag reduction is essentially different from that of riblets.
ROBUST FEEDBACK LINEARIZATION CONTROL OF A THROTTLE PLATE BY USING AN APPROXIMATED PD REGULATOR

Abstract In classical gasoline injection systems, the control of the throttle plate position is important for efficiency and emission of the engine. The angular position, depending on the current load of the engine, must track a desired trajectory which is performed by the accelerator. In Feedback linearization approach the state space must be available: measurable or observable. If the system is nonlinear, observers of the state in real time application are often difficult to be implemented. A technique to approximate derivatives is proposed in order to avoid velocity and acceleration measurements. The tracking problem is treated by using Kharitonov's approach. Thanks to an approximated PD regulator robustness in the proposed feedback linearization is achieved. Measured results on the real experimental set point are reported.
The very first step to start psychophysical experiments

This tutorial article aims to guide the reader to learn about three types of psychophysical methods: the method of adjustment, the method of limits and the method of constant stimuli. The article explains how to estimate the point of subjective equality and the just noticeable difference with each method. It also explains about pitfalls that one may encounter when designing experiments. Results could be distorted by some bias effects that are due to technical procedures adopted for experiments. One should know where these effects are likely to occur.
Periodic solutions for nonlinear systems with p-Laplacian-like operators

Let us consider the so-called one-dimensional p-Laplacian operator (,p(u$))$, where p>1 and ,p : R R is given by ,p(s)=|s| p&2 s for s{0 and ,p(0)=0. Various separated two-point boundary value problems containing this operator have received a lot of attention with respect to existence and multiplicity of solutions. See, for example, [3, 9, 11, 13, 21, 22, 28, 31, 33], and the references therein. Periodic boundary conditions have been considered in [12, 14]. The case of separated two-point boundary conditions when ,p is replaced by a one-dimensional possibly not homogeneous operator ,, has been dealt with in a series of papers, cf. [2, 8, 15, 16, 17, 18, 19]. Our aim in this paper is to study existence of periodic solutions to some system cases involving the fairly general vector-valued operator ,. Thus we will consider the boundary value problem
Delay‐dependent H∞ control of linear discrete‐time systems with time‐varying delay via switched system approach

This paper deals with the problem of H∞ control of linear discrete‐time systems with time‐varying delay. In order to highlight the relations between all combinations of delayed states, a general Lyapunov–Krasovskii functional is introduced, from which the relation between the switched system transformation and the classical Lyapunov–Krasovskii method is established. The basic idea is to formulate the original time‐delay systems as switched systems with arbitrary switching. Therefore, the stability and the H∞ performance problems can be reduced to the corresponding problems of such switched systems. This fact bridges two distinct research fields. Finally, numerical examples are given to illustrate the effectiveness of the method and its advantage over existing results. Copyright © 2009 John Wiley & Sons, Ltd.
Graphs on uniform points in [0,1]d

Statistical problems in pattern or structure recognition for a random multidimensional point set may be addressed by variations on the random graph model of Erdos and Renyui. The imposition of graph structure with a variable edge criterion on a large random point set allows a search for signature quantities or behavior under the given distributional hypothesis. The work is motivated by the question of how to make statistical inferences from sensed mine field data. This article describes recent results obtained in the following special cases. On independent random points U1,. ,Un distributed uniformly on [0,1]d, a random graph Gn(x) is constructed in which two distinct such points are joined by an edge if the l(infinity )-distance between them is at most some prescribed value 0 n, the smallest x such that Gn(x) is connected, and the largest nearest neighbor link dn, the smallest x such that Gn(x) has no vertices of degree zero, are asymptotic in ratio, as n becomes large, for d >= 2.
Existence of positive solutions to an elliptic system with coupled nonlinearity

In this article, we study weakly coupled systems of elliptic equations without Hamiltonian structure in both bounded domain and the whole space. By using a priori estimates, Pohozaev identity and degree theory, we are able to show the existence of positive solutions. Dedicated to Prof. Zuhair Nashed.
MORPHOLOGICAL DISTORTION OF GALACTIC GLOBULAR CLUSTERS

The shapes and sizes of 116 Galactic globular clusters (GCs) are presented, based on the analysis of the spatial distribution of 2MASS point sources. In general, Galactic GCs are slightly flattened in shape, with a median axial ratio of 0.87. The GCs close to the Galactic bulge have various degrees of flattening, and those exhibiting obvious flattening tend to have their elongation pointing toward the Galactic center, manifesting the tidal effect from the bulge. In comparison, GCs away from the Galactic center tend to be spherical. A few GCs in the halo are also found to have elongated shape. Three notable cases of highly flattened clusters were previously known to be associated with stellar streams or particular dynamical history: NGC 5897 is known to have a stellar tidal tail extending to its equatorial north and south; NGC 6838 had a recent encounter with the Galactic plane; and IC 4499 is spatially close to, and collimated with, the “Magellanic Stream. ” We also found 31 GCs associated with possible clumpy structures in stellar distributions, as diagnosed by possible cluster members selected by colors and magnitudes. Four such cases of stellar debris are presented: NGC 6366 is experiencing heavy tidal stripping and NGC 2808 has been known to have multiple main-sequence branches. NGC 3201 and NGC 6397, like the flattened cluster, NGC 6838, also have their recent passage through the Galactic plane. Our sample is derived from the most inclusive analysis of the morphology of Galactic GCs, and should provide a valuable database to probe the mass distribution, or merging history of the Milky Way galaxy.
Recursive estimation for hidden Markov models: a dependent case

A discrete time, finite state Hidden Markov Model is considered. This consists of a Markov chain and a finite state observation process. A recent paper considered the case when the noises in the chain and the observation process are independent; this paper discusses the more complicated dependent case. Recursive conditional normalized and unnormalized, (Zakai), estimates are obtained for: the state of the chain, the number of jumps of the chain from one state to another, the occupation time of the chain in any state, the number of transitions of the observation process and the number of joint transitions of the chain and observation process. These results allow reestimation of the parameters of the model. In particular, they provide a test for whether the noise terms in the chain and observation are independent
Pattern formation in the flow of thin films down an incline: Constant flux configuration

We present fully nonlinear time-dependent simulations of a thin liquid film flowing down an inclined plane. Within the lubrication approximation, and assuming complete wetting, we find that varying the inclination angle considerably modifies the shape of the emerging patterns: Finger-shaped patterns result for the flow down a vertical plane, while saw-tooth patterns develop for the flows down an inclined plane. However, in all of our simulations, the roots always move, indicating that the shape of the patterns is not necessarily related to the surface coverage, a technologically important feature of the flow. Furthermore, we find that triangular steady-state patterns may be produced for the flow down an incline, while the fingers typically grow in length for all explored times. We find quantitative agreement with reported experiments, and suggest new ones.
A Study of Baroclinic Wave Behavior over Bottom Topography Using Complex Principal Component Analysis of Experimental Data

Abstract Complex principal component analysis is applied to data from three laboratory experiments of flow over two-wave sinusoidal bottom topography in a thermally driven, rotating annulus of fluid. The experiments are conducted at the same imposed temperature contrast (ΔT) and at three different rotation rates (Ω). In each case, the intensity of the wave activity is maximum downstream of the two topographic ridges. The analysis, however, reveals a fundamental difference in the behavior of the waves at lower rotation rates than at the highest rotation rate. At the lower Ω's, the baroclinic waves travel over the topographic ridges with diminished intensity and amplify on the other side of each ridge, with the result that the flows downstream of the two ridges are coherent. At the largest Ω, at which the Rossby number, Ro, is very small and the friction parameter, r = E½/Ro (where E is proportional to the Ekman number), is rather large, the waves downstream of each ridge are decoupled from those downstream.
Reconstruction d'une source lumineuse modélisée par une quadrique à partir d'images multiples

Reconstruire les sources lumineuses peut ameliorer de facon significative le rendu des applications de realite augmentee (RA) et contribuer a une meilleure comprehension de la scene, a la reconstruction 3D et a la localisation de camera. Les approches existantes se focalisent sur l'estimation d'illumination et de radiance sans prendre en compte la geometrie des sources lumineuses. Notre methode propose une reconstruction 3D de sources lumineuses en interieur a partir des specularites. Les quadriques sont utilises comme un nouveau modele de lumiere a forme generique pouvant representer une ampoule ou encore un neon ce qui n'est pas possible avec l'etat de l'art actuel. A partir d'au moins trois points de vue contenant des specularites, une quadrique est reconstruite en estimant des coniques pour chaque specularite. Cette estimation initiale est raffinee par la suite en reduisant la distance entre les coniques issues de la projection de la quadrique pour chaque point de vue et le contours des specularites associees.
The Hilbert Transform on Rearrangement-Invariant Spaces

The purpose of this paper is to investigate conditions under which the Hilbert transform defines a bounded linear operator from a given function space into itself. The spaces with which we deal have the property of rearrangement-invariance which is defined in §1. This class of spaces includes the Lebesgue, Orlicz, and Lorentz spaces.
Optical identification of the transient X-ray source A1524 – 61

Since the decay of the highly successful X-ray observatory on board the "Einstein" satellite, things have been relatively quiet concerning discoveries on the X-ray sky. For some time, the scene was dominated by the tiny Japanese satellite Hakucho. This spacecraft carried no imaging detectors, but turned out to be very useful for the study of already known, relatively bright sources. At ESO, we used much observing time simultaneously with Hakucho in an attempt to learn more about the so-calied X-ray burst sources (1). Recently, two more X-ray satellites have been launched: the second Japanese satellite, TENMA, and the European EXOSAT. Most of the observations with these satellites are planned in advance, but, as is the case with ground-based observations, the temporary appearance of a new celestial object may justify a change of schedule. This is what happened on August 18, 1983, when the transient source monitor on board TENMA detected a bright, new X-ray source near the border between the southern constellations Lupus and Norma. Three days later the source had reached half the brightness of Sco X-1 , wh ich may be called the "Sirius" of the X-ray sky. At La Silla, we were immediately alerted by telex in order that we could try to identify the source optically, but during just those days, odds were against any optical work. Full moon was approaching, and the Schmidt telescope was out of operation because of technical Work. Or. Tanaka, from the TENMA team, had, however, remarked that the new source appeared very close to the Position of a bright X-ray transient which had been seen from July 1971 till September 1972 by the Uhuru satellite. This Source, called 4U1543-47 (2), had never been identified optically. We immediately checked our CCO data bank for pictures of the former transient position. Indeed, CCO pictures had been taken in July 1981 during the installation period ofthe CCO camera at the 1.5 m Oanish telescope. Prior analysis of these images (which were taken in three colours) had shown no object of conspicuous colours. The images were checked once more, but with the same result. The location of the old transient was, however, not known to great accuracy, and it could, indeed, be outside the area covered by the CCO.
COMPUTATION OF THE RELAXATION OSCILLATION PERIOD IN LOTKA‐VOLTERRA SYSTEMS

ABSTRACT. This work surveys techniques of Grasman and Veling [1973], Vasil'eva and Belyanin [1988] and Shih [1996] for computing the relaxation oscillation period of singularly perturbed Lotka‐Volterra systems. Grasman and Veling [1973] used an implicit function theorem to derive an asymptotic formula for the period; Vasil'eva and Belyanin [1988] employed a method of matched asymptotic expansions to obtain an approximation to the period; Shih [1996] obtained two (exact) integral representations for the period in terms of two inverse functions W(–k, x) of xexp(x). These results are compared numerically and asymptotically. In particular, the integral representation of the period in Shih [1996] is computed numerically using a Gauss‐Tschebyscheff integration rule of the first kind, and is further investigated asymptotically by virtue of the asymptotics of W(–k, x), Laplace's method, and a method of consequent representation. Computational results indicate that the Gauss‐Tschebyscheff approximation of the period in Shih [1996] is uniformly accurate for a wide range of the singular parameter (ɛ in the paper).
Measurement Error Models with Auxiliary Data

We study the problem of parameter inference in (possibly non-linear and non-smooth) econometric models when the data are measured with error. We allow for arbitrary correlation between the true variables and the measurement errors. To solve the identification problem, we require the existence of an auxiliary data-set that contains information about the conditional distribution of the true variables given the mismeasured variables. Our main assumption requires that the conditional distribution of the true variables given the mismeasured variables is the same in the primary and auxiliary data. Our methods allow the auxiliary data to be a validation sample, where the primary and validation data are from the same distribution, and more importantly, a stratified sample where the auxiliary data-set is not from the same distribution as the primary data. We also show how to combine the two data-sets to obtain a more efficient estimator of the parameter of interest. We establish the large sample properties of the sieve based estimators under verifiable conditions. In particular, we allow for the mismeasured variables to have unbounded supports without employing the tedious trimming scheme typically used in kernel based methods. We illustrate our methods by estimating a returns to schooling censored quantile regression using the CPS/SSR 1978 exact match files where the dependent variable is measured with error of arbitrary kind. Copyright 2005, Wiley-Blackwell.
Association Schemes and Directed Graphs Determined by Orbitals of General Linear Groups Over Finite Chain Rings

Let R be a finite commutative chain ring, 1 ≤ k ≤ n − 1, the set of right invertible k × n matrices, and GL n (R) the general linear group of degree n over R, respectively. It is clear that Q ↦ QU ( , U ∈ GL n (R)) is a transitive action on and induces the diagonal action of GL n (R) on defined by (Q 1, Q 2)U = (Q 1 U, Q 2 U) for and U ∈ GL n (R), which are then subdivided into orbits under the action of GL n (R). First, we investigate the three questions: (i) How should the orbits be described? (ii) How many orbits are there? (iii) What are the lengths of the orbits? Then we compute parameters of the association scheme on and give precisely the structures of directed graphs determined by the orbits of diagonal action of GL n (R) on .
Collaborater for a Car‐Like Vehicle Driven by a User with Visual Inattention

This paper proposes a control system applied to a car‐like vehicle driven by a user. The controller is designed to mitigate the negative effects produced by possible visual distractions of this user. In addition, the paper proposes to evaluate the user's visual distraction, defining a vector that has two components: one with respect to the path and the other with respect to the obstacles. These elements can be computed on‐line and are associated with two time delays that produce a similar effect of instability on the motion of the vehicle. The proposed scheme considers the distraction in the design through such delays. Finally, experiments using a car simulator are carried out
Sensitivity of plume dynamics to the parameterization of vertical mixing

A three-dimensional primitive equation, baroclinic numerical model incorporating a range of turbulence closure schemes is used to investigate the effects of vertical diffusion of momentum and density upon the spread of a freshwater plume, with particular reference to the Ebro plume. Initial calculations show that there are some differences in the horizontal spread and vertical mixing of the plume when diffusion coefficients are computed from a two-equation turbulence energy model compared with a one-equation model. To understand results from the turbulence energy models, the sensitivity of the plume dynamics to variations in the coefficient of vertical eddy viscosity and diffusivity is also considered, with increases in these parameters having a significant effect upon the cross-shore and along-shore spread of the plume. Also, increasing these parameters changes the plume characteristics from supercritical to subcritical and reduces the occurrence of meandering and baroclinic instability along the plume's off-shore edge. However, differences in the southerly spread (the direction of Kelvin wave propagation in the model) of the plume (although not its northerly spread) produced by changes in diffusion coefficients are small compared with the influence of changes in the bottom slope, upon the along-shore southerly spread of the plume, which moves in the direction of Kelvin wave propagation in the near coastal region. Results from the series of calculations are used as a guide in experimental design, with reference to a planned experiment in the Ebro region involving a coastal HF Radar deployment, as well as off-shore measurements. Calculations suggest that surface current measurements from a coastal HF Radar, together with a detailed survey of the density field associated with the plume, may be an appropriate, although indirect, means of determining suitable mixing coefficients to use in plume discharge problems. Detailed measurements of water depth variation will also be required. Copyright © 1999 John Wiley & Sons, Ltd.