Miracle-dz/UniFAR-FTUs huggingface dataset:
Continuum Mechanics and Theory of Materials

1 Kinematics. - 2 Balance Relations of Mechanics. - 3 Balance Relations of Thermodynamics. - 4 Objectivity. - 5 Classical Theories of Continuum Mechanics. - 6 Experimental Observation and Mathematical Modelling. - 7 General Theory of Mechanical Material Behaviour. - 8 Dual Variables. - 9 Elasticity. - 10 Viscoelasticity. - 11 Plasticity. - 12 Viscoplasticity. - 13 Constitutive Models in Thermomechanics. - References.
A simple controller for unknown nonlinear systems

This work addresses the dynamic feedback control problem of unknown nonlinear systems that can be affected by unknown state and control dependent perturbations (that can appear, for instance, as result of unexpected changes of system dynamics due to faults). To include the perturbations, unknown general nonlinear systems are considered. By using bounded linearly parameterized approximators to parameterized the unknown nonlinearities, a controller that guarantees uniform ultimate boundedness of all signals in closed loop is designed. The proposed controller forces the tracking error to converge to a ball whose radius can be a priori arbitrary specified by the control designer. Simulation results shows the effectiveness and feasibility of the proposed scheme.
Numerical Simulation of Mechanical Behaviour of Textile Surfaces

The paper presents a model which can be used for calculations of complex mechanical behaviour of textile surfaces e.g. surfaces obtained from a drapemeter. Fabric is treated an this model as a two‐dimensional continuum. As kinetic and kinematic measures are used these of the Cosserat continuum. Linear elastic, orthotropic constitutive equations which enable independent treatment of the in plane and out of plane deformations, describe material behaviour of the textile structure.
Bayesianism and Unification: A Reply to Wayne Myrvold*

Myrvold (2003) has proposed an attractive Bayesian account of why theories that unify phenomena tend to derive greater epistemic support from those phenomena than do theories that fail to unify them. It is argued, however, that “unification” in Myrvold's sense is both too easy and too difficult for theories to achieve. Myrvold's account fails to capture what it is that makes unification sometimes count in a theory's favor.
Comparison Study of Subspace Identification Methods Applied to Flexible Structures

Abstract In the past few years, various time domain methods for identifying dynamic models of mechanical structures from modal experimental data have appeared. Much attention has been given recently to so-called subspace methods for identifying state space models. This paper presents a detailed comparison study of these subspace identification methods: the eigensystem realisation algorithm with observer/Kalman filter Markov parameters computed from input/output data (ERA/OM), the robust version of the numerical algorithm for subspace system identification (N4SID), and a refined version of the past outputs scheme of the multiple-output error state space (MOESP) family of algorithms. The comparison is performed by simulating experimental data using the five mode reduced model of the NASA Mini-Mast structure. The general conclusion is that for the case of white noise excitations as well as coloured noise excitations, the N4SID/MOESP algorithms perform equally well but give better results (improved transfer function estimates, improved estimates of the output) compared to the ERA/OM algorithm. The key computational step in the three algorithms is the approximation of the extended observability matrix of the system to be identified, for N4SID/MOESP, or of the observer for the system to be identified, for the ERA/OM. Furthermore, the three algorithms only require the specification of one dimensioning parameter.
Theory and numerics for finite deformation fracture modelling using strong discontinuities

A general finite element approach for the modelling of fracture is presented for the geometrically non‐linear case. The kinematical representation is based on a strong discontinuity formulation in line with the concept of partition of unity for finite elements. Thus, the deformation map is defined in terms of one continuous and one discontinuous portion, considered as mutually independent, giving rise to a weak formulation of the equilibrium consisting of two coupled equations. In addition, two different fracture criteria are considered. Firstly, a principle stress criterion in terms of the material Mandel stress in conjunction with a material cohesive zone law, relating the cohesive Mandel traction to a material displacement ‘jump’ associated with the direct discontinuity. Secondly, a criterion of Griffith type is formulated in terms of the material‐crack‐driving force (MCDF) with the crack propagation direction determined by the direction of the force, corresponding to the direction of maximum energy release. Apart from the material modelling, the numerical treatment and aspects of computational implementation of the proposed approach is also thoroughly discussed and the paper is concluded with a few numerical examples illustrating the capabilities of the proposed approach and the connection between the two fracture criteria. Copyright © 2005 John Wiley & Sons, Ltd.
Choosing the renormalization/factorization scale (QCD)

The basic issue is that all perturbative calculations involve a truncated expansion. For calculations to have predictive power, one must have some idea of the errors due to omission of uncalculated terms. In typical QCD calculations, the problem is compounded by the presence of an arbitrary scale parameter, mu . Without some knowledge of an appropriate range of values for the scale parameter, perturbative QCD calculations are without predictive power. Finally, a very prevalent subtraction scheme is minimal subtraction, the MS scheme, where the scale parameter has no manifest physical interpretation.
Shallow-Water Flow past Isolated Topography. Part II: Transition to Vortex Shedding

Abstract The formation of Karman vortex streets is studied within the framework of single-layer shallow-water dynamics and in absence of surface friction and background rotation. In the first part of this study, steady numerical solutions for flow past circular topography were obtained by imposing a symmetry condition that essentially suppressed vortex shedding. In the second part, this symmetry condition is relaxed in order to study the transition into the vortex-shedding regime. This transition is due to an instability of the symmetric wake pattern. The most unstable global normal mode of this instability is derived by a numerical method. Most of the features of this mode can be understood in terms of the absolute instability theory. The mode is essentially barotropic and relies on a positive feedback between the perturbations located on the two shearlines on either side of the wake. The classical shear modes centered on a single shearline are, on the other hand, shown to be absolutely stable even thoug.
Determination of the mass of globular cluster X-ray sources

On a mesure avec l'observatoire RX Einstein les positions precisions (∼1'') des sources RX lumineuses dans 8 amas globulaires. La distribution des masses des sources RX se situe entre 0,9 et 1,9 M ○. Les positions des sources RX et les etudes optiques detaillees indiquent que les sources sont probablement toutes de meme masse (∼1,5 M ○. ), que les potentiels gravitationnels dans ces amas a haute densite centrale sont relativement lisses et isothermes et que les sources RX sont des binaires compactes et sont probablement formees par capture tidale
Application of the Morse Potential Function to Cubic Metals

The Morse parameters for the pairwise interaction of atoms in cubic metals were calculated from experimental values of the energy of cohesion, the lattice constant, and the compressibility. The equation of state and the elastic constants computed from the Morse parameters were shown to be in agreement with experiment. The Born stability conditions were also satisfied by both the facecentered and body-centered metals. The Morse function thus was found to be applicable to problems involving any type of deformation of the cubic metals. (auth)
CO observations of infrared bright galaxies - The efficiency of star formation

CO emission has been detected in each of 14 of the IR-bright galaxies listed in IRAS Circular 15; for the nine galaxies of the largest angular size, the CO emission distributions along the major axis have been mapped. A strong correlation is noted between total CO luminosities and IR ones for galaxies in each of three ranges of dust temperature. The ratio of IR/CO luminosities increases with the ratio of 60/100-micron flux densities, consistent with emission of thermal origin at the characteristic temperature given by the dust temperature. If this luminosity ratio is a measure of the emergent stellar luminosity/unit molecular mass, or the efficiency of star formation, this efficiency varies over almost two orders of magnitude from one galaxy to another.
CUSUM chart for detecting range shifts when monotonicity of likelihood ratio is invalid

It is often encountered in the literature that the log-likelihood ratios (LLR) of some distributions (e.g. the student t distribution) are not monotonic. Existing charts for monitoring such processes may suffer from the fact that the average run length (ARL) curve is a discontinuous function of control limit. It implies that some pre-specified in-control (IC) ARLs of these charts may not be reached. To guarantee the false alarm rate of a control chart lower than the nominal level, a larger IC ARL is usually suggested in the literature. However, the large IC ARL may weaken the performance of a control chart when the process is out-of-control (OC), compared with a just right IC ARL. To overcome it, we adjust the LLR to be a monotonic one in this paper. Based on it, a multiple CUSUM chart is developed to detect range shifts in IC distribution. Theoretical result in this paper ensures the continuity of its ARL curve. Numerical results show our proposed chart performs well under the range shifts, especially under the large shifts. In the end, a real data example is utilized to illustrate our proposed chart.
Detection, Localization, and Tracking of Shock Contour Salient Points in Schlieren Sequences

Computer vision methods are proposed for feature extraction of structures of interest in schlieren images. The well studied curvature scale space is used to define features at physically salient points on shock contours. These points can include shock interactions, reflections, standoff distance, etc., and are present in many schlieren data. A challenge in developing methods for feature extraction in schlieren images is the reconciliation of existing techniques with structures of interest to an aerodynamicist. Domain-specific knowledge of physics must be incorporated into the definition and detection phases. Algorithms must be designed such that incorporation of an aerodynamic knowledge base is viable and known location and physically possible structure representations form a knowledge base that provides a unique feature definition and extraction. Model tip location and a shock intersection across several thousand frames in the complex double-cone schlieren sequence are identified, localized, and tracked.
TRAFFIC PERFORMANCE AT URBAN STREET INTERSECTIONS

A PRELIMINARY EXPLORATION WAS CONDUCTED INTO THE FUNDAMENTAL RELATIONSHIPS WHICH EXIST BETWEEN TRAFFIC UNITS. METHODS AND THE MORE COMMONLY OBSERVED TRAFFIC PHENOMENA OF ACCELERATION AND DECELERATION WERE OBSERVED. THE SEVERAL COMPONENTS OF THE PERFORMANCE OF VEHICLE STARTING AT URBAN INTERSECTIONS WERE INVESTIGATED. REACTION TIMES TO THE LIGHT CHANGE AND BETWEEN VEHICLES WERE FOUND TO BE IN SOME MEASURE DEPENDENT ON PEDESTRIAN MOVEMENT. SEVERAL METHODS OF PRESENTING STARTING-TIME-DISTANCE PERFORMANCE WERE USED FOR THE SAKE OF CLARITY. THE TIME-DISTANCE RELATIONSHIPS AT START PROVED TO BE SIMILAR AT THE DIFFERENT INTERSECTIONS STUDIED. TWO METHODS FOR DETERMINING THEORETICAL INTERSECTION CAPACITY WERE PRESENTED AND THEIR PRACTICAL APPLICATION DISCUSSED. IT IS CONCLUDED THAT A VERY SMALL PERCENTAGE OF DECELERATIONS IN ACTUAL PRACTICE REACH THE POSSIBLE MAXIMUM. THERE ARE TWO TYPES OF DECELERATION, THE FUNCTIONAL, AND WHAT HAS BEEN CALLED CHRONOTROPIC. NO TIME IS LOST DUE TO NOT TAKING ADVANTAGE OF MAXIMUM DECELERATION IN THE LATTER TYPE. THE TRAFFIC DELAY IN URBAN AREAS IS NOT CLOSELY RELATED TO THE RATES OF DECELERATION EMPLOYED SINCE MOST STOPS ARE OF A CHRONOTROPIC NATURE. A TECHNIQUE OF TIME-SPACING ANALYSIS IS APPLIED TO TRAFFIC BEHAVIOR AT NON- CONTROLLED INTERSECTIONS. PHYSICAL CHARACTERISTICS OF THE INTERSECTION AFFECT THE BEHAVIOR OF THE DRIVERS INSOFAR AS THEIR ABILITY TO MAKE EARLY DECISIONS AND AVOID DELAY IN CROSSING IS CONCERNED. THERE IS A TENDENCY AT THE NON- CONTROLLED INTERSECTIONS FOR THE MAJOR STREAM OF TRAFFIC TO BE AGGRESSIVE AND TO FORCE THE MINOR TO GIVE WAY. IN GENERAL, TIME-SPACE RELATIONSHIPS GOVERN THE BEHAVIOR OF MOTORISTS AT UNSIGNALIZED INTERSECTIONS. ROAD TRAFFIC CONFORMS SO WELL TO POISSON'S RANDOM SERIES THAT ITS APPLICATION LEADS TO RESULTS OF PRACTICAL IMPORTANCE. IT IS POSSIBLE TO DETERMINE DELAY AT SIGNALIZED INTERSECTIONS THROUGH THE USE OF POISSON'S FORMULA. A THEORETICALLY CORRECT METHOD HAS BEEN DEVELOPED. THE THEORY, IN REGARD TO SIGNALS WHICH FAIL TO CLEAR SOME VEHICLES RETARDED DURING THE RED PERIOD, IS DEVELOPED SINCE POISSON'S FORMULA IS APPLICABLE TO THIS PROBLEM AS WELL. THE TRAFFIC PROBLEM TREATMENT BY PROBABILITY THEORY AND OTHER PRINCIPALS DEVELOPED IN THIS STUDY ARE ONLY EXEMPLARY OF A VARIETY OF APPLICATIONS.
Ab Initio Direct Trajectory Simulation with Nonadiabatic Transitions of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN + H

The dissociative recombination reaction of HCNH+ + e- via indirect radiative mechanism on relevant excited state potential energy surfaces has been studied to investigate the branching ratio of the products, HNC/HCN, by using an ab initio direct trajectory method at the state-averaged multiconfigurational self-consistent field level. In trajectory simulations using adiabatic potential energy surfaces, nonadiabatic transitions among the three electronic states of HCNH, i.e., 1 2Π, 1 2Σ+, and 2 2Σ+, were explicitly treated by Tully's surface-hopping algorithm. We show that HNC and HCN are produced with almost the same ratio from this reaction, supporting the picture that HCNH+ plays a significant role as the precursor for both HNC and HCN production in interstellar clouds.
Laboratory experiments and a non-harmonic theory for topographic Rossby waves over a linearly sloping bottom on the f-plane

Low-frequency waves that develop in a shallow layer of fluid, contained in a channel with linearly slopping bottom and rotating with uniform angular speed are investigated theoretically and experimentally. Exact numerical solutions of the eigenvalue problem, obtained from the linearized shallow water equations on the f-plane, show that the waves are trapped near the channel's shallow wall and propagate along it with the shallow side on their right in the Northern hemisphere. The phase speed of the waves is slower compared with that of the harmonic theory in which bottom slope is treated inconsistently. A first-order approximation of the cross-channel dependence of the coefficient in the eigenvalue equation yields an approximation of the cross-channel velocity eigenfunction as an Airy function, which, for sufficiently wide channels, yields an explicit expression for the wave's dispersion relation. The analytic solutions of the eigenvalue problem agree with the numerical solutions in both the wave trapping and the reduced phase speed. For narrow channels, our theory yields an estimate of the channel width below which the harmonic theory provides a more accurate approximation. Laboratory experiments were conducted on a 13 m diameter turntable at LEGI-Coriolis (France) into which a linearly sloping bottom of 10 % incline was installed. A wavemaker generated waves of known frequency at one end of the turntable and the wavenumbers of these waves were measured at the opposite end using a particle imaging velocimetry technique. The experimental results regarding the phase speed and the radial structure of the amplitude are in very good agreement with our theoretical non-harmonic predictions, which support the present modification of the harmonic theory in wide channels.
Thermal and dynamic evolution of a spherical bubble moving steadily in a superheated or subcooled liquid

The heat transfer rate and the hydrodynamic forces experienced by a single vapor bubble of variable radius moving in a superheated or subcooled liquid are studied by means of numerical simulation. For that purpose the full Navier–Stokes equations and the temperature equation are solved in a frame of reference where the bubble surface is steady. The time evolution of the bubble radius is determined by solving the energy balance at the bubble surface. The numerical method is first validated by comparing present predictions with previous asymptotic or numerical results in the case where no relative motion between the liquid and the bubble exists. Then the situation where a constant relative velocity exists is considered. Effects of the mean flow on the heat transfer rate and on the bubble radius evolution are first discussed. Two different stages are generally observed in the computations. First, the radial motion induced by the displacement of the bubble surface dominates and the bubble evolution is essenti.
Exciton States and Band Structure in CdS and CdSe

The theoretical effects of a finite slope condition band crossing on the direct exciton energy levels of wurtzite compounds is investigated. The lack of an experimental confirmation of these effects places an upper limit of about 10−10 ev‐cm on the slope of the conduction band at k = 0 in CdS, and a slightly larger limit in CdSe. Theoretical estimates of these slopes are also calculated. Another possible method of observing the magnetic effects due to the nonzero wave vector of the excitons is noted. The striking increase of the exciton oscillator strength in CdSe in a magnetic field is attributed to the magnetic compression of the excitons. A brief comparison of experimental energy band parameters for CdS and CdSe is given.
A Method for Simulating Stable Random Variables

Abstract A new algorithm is presented for simulating stable random variables on a digital computer for arbitrary characteristic exponent α(0 < α ≤ 2) and skewness parameter β(-1 ≤ β ≤ 1). The algorithm involves a nonlinear transformation of two independent uniform random variables into one stable random variable. This stable random variable is a continuous function of each of the uniform random variables, and of α and a modified skewness parameter β' throughout their respective permissible ranges.
Time–Frequency Localization and the Spectrogram

Abstract One method by which the time–frequency content of a signal can be measured is by the Gabor (or windowed Fourier) transform. It is defined as the Fourier transform of the product of the signal against a translate of a fixed window function. Multiplication by the window localizes the signal in time, and hence the Fourier transform computes the spectrum of the signal localized in time. The magnitude squared of the Gabor transform is known as the spectrogram of the signal. In this paper, we are concerned with the problem of finding signals that are maximally concentrated within a given region of phase space. It is well known that such problems give rise to an integral eigenvalue problem for an associated concentration operator. It is easy to see that such an operator is positive self-adjoint, with eigenvalues bounded above by one. In this paper, we show that for a bounded measurable domain and for the gaussian window function, the eigenfunctions of such a concentration operator with nonzero eigenvalue are analytic and of exponential decay, while the eigenvalues decay exponentially in the index. Furthermore, the number of eigenvalues close to unity is asymptotically equal to the measure of the domain, upon dilation. With some regularity assumptions on the domain, we also prove that the number of eigenvalues strictly between zero and one grows at most linearly in the dilation factor. These results are sensitive to the regularity of the window function.
BIPM direct on-site Josephson voltage standard comparisons: 20 years of results

The discovery of the Josephson effect has for the first time given national metrology institutes (NMIs) the possibility of maintaining voltage references which are stable in time. In addition, the introduction in 1990 of a conventional value for the Josephson constant, KJ-90, has greatly improved world-wide consistency among representations of the volt. For 20 years, the Bureau International des Poids et Mesures (BIPM) has conducted an ongoing, direct, on-site key comparison of Josephson voltage standards among NMIs under the denominations BIPM.EM-K10.a (1 V) and BIPM.EM-K10.b (10 V) in the framework of the mutual recognition arrangement (CIPM MRA). The results of 41 comparisons illustrate the consistency among primary voltage standards and have demonstrated that a relative total uncertainty of a few parts in 1010 is achievable if a few precautions are taken with regard to the measurement set-up. Of particular importance are the grounding, efficient filters and high insulation resistance of the measurement leads, and clean microwave distribution along the propagation line to the Josephson array. This paper reviews the comparison scheme and technical issues that need to be taken into account to achieve a relative uncertainty at the level of a few parts in 1010 or even a few parts in 1011 in the best cases.
Geometrical Analysis of Avalanches in a 2D Drum

We present an experimental and numerical analysis of intermittent flow at the surface of a 2-dimensional granular medium. Two types of devices are used: a 2-dimensional drum and a long rectangular box. Two types of grains are used (disks and pentagons), and comparison is made between the different cases. The experimental data are compared with the results obtained from molecular dynamics simulations, using roughly the same number of particles. Dynamical conditions of stability are determined from the angle of repose θ r and the angle of maximum stability θ m . Intermittent flow at the «surface» appears to be of two types, as in 3-dimension: small avalanches whose time fluctuations are characterised by a power spectrum obeying a power law, and large events with well-defined average size and duration time
Electrical spin accumulation with improved bias voltage dependence in a crystalline CoFe/MgO/Si system

We report the electrical spin accumulation with enhanced bias voltage dependence in n-type Si, employing a crystalline CoFe/MgO tunnel contact. A sizable spin signal of ∼4.8 kΩμm2, a spin lifetime of ∼155 ps, and a spin diffusion length of ∼220 nm were obtained at 300 K. The spin signal and lifetime obtained in this system show consistent behavior with the temperature variation irrespective of the bias voltage. Notably, the spin signal exhibits nearly symmetric dependence with respect to the bias polarity, which is ascribed to the improved bias dependence of tunnel spin polarization.
Global stabilization of a PVTOL aircraft model with bounded inputs

We propose a global stabilizing control design for the planar vertical takeoff and landing (PVTOL) aircraft, with bounded inputs. The approach is based on the use of non-linear combinations of linear saturation functions bounding the thrust input and the rolling moment to arbitrary saturation limits. We provide global convergence of the state to the origin, using a relatively simple algorithm.