Miracle-dz/UniFAR-FTUs huggingface dataset:
Vibration of a Temperature-Dependent Thermally Pre/Postbuckled FGM Beam Over a Nonlinear Hardening Elastic Foundation

Small amplitude vibrations of a functionally graded material beam under in-plane thermal loading in the prebuckling and postbuckling regimes is studied in this paper. The material properties of the FGM media are considered as function of both position and temperature. A three parameters elastic foundation including the linear and nonlinear Winkler springs along with the Pasternak shear layer is in contact with beam in deformation, which acts in tension as well as in compression. The solution is sought in two regimes. The first one, a static phase with large amplitude response, and the second one, a dynamic regime near the static one with small amplitude. In both regimes, nonlinear governing equations are discretized using the generalized differential quadrature (GDQ) method and solved iteratively via the Newton–Raphson method. It is concluded that depending on the type of boundary condition and loading type, free vibration of a beam under in-plane thermal loading may reach zero at a certain temperature which indicates the existence of bifurcation type of instability.
Sequential Monte Carlo implementation and state extraction of the group probability hypothesis density filter for partly unresolvable group targets-tracking problem

This study proposes a sequential Monte Carlo (SMC) implementation to the Mahler's group probability hypothesis density filter (PHDF) for partly unresolvable group targets tracking problem. A potential limitation of the group PHDF is that it cannot be used to determine the number of groups. Therefore we have to jointly extract the group number and states from the proposed group SMC-PHDF at each time step. We propose to fit the resampled particles of the group SMC-PHDF by application of Gaussian mixture models with unknown component number. In the mixture, the number and parameters of the components correspond to the number and states of the groups over the observation region. The Markov chain Monte Carlo (MCMC) algorithm is proposed to estimate the component parameters of the mixture. The estimate of component number of the mixture can be derived by a component management strategy. In simulation, the proposed group SMC-PHDF with the expectation maximum (EM) and MCMC extractions are, respectively, used to detect and track the groups. Hundred Monte Carlo simulation results show that the latter outperforms the former a lot in estimating the group number and states, although the computational requirement of the MCMC extraction is more expensive than the EM extraction.
Viscous instability of a sheared liquid-gas interface: Dependence on fluid properties and basic velocity profile

In the framework of linear stability theory, we analyze how a liquid-gas mixing layer is affected by several parameters: viscosity ratio, density ratio, and several length scales. These scales reflect the presence of a velocity defect induced by the wake behind the splitter plate and the presence of boundary layers which develop ahead of the plate trailing edge. Incorporating such effects, we compute the various temporal and spatial instability modes and identify their driving instability mechanism based on their Reynolds number dependence, spatial structure, and energy budget. It is examined how the velocity defect modifies the temporal and the spatial stability properties. In addition, the transition from convective to absolute instability occurs at lower velocity contrast between gas and liquid free streams when a defect is present. This transition is also promoted by surface tension. Compared to inviscid stability computations, our spatial stability analysis displays a better agreement with measured growth rates obtained in two recent air-water experiments.
Extended study of Poynting theorem and reciprocity on nonuniform FDTD meshes

The physical mechanisms behind numerical errors arising on nonuniform FDTD meshes are revealed and evaluated, focusing on the basic step-in-cell-size mesh nonuniformity and standard as well as compensated FDTD algorithms. Beginning with rigorous derivations of mathematical formulas for the numerical reflection coefficient, it is shown that wave impedance for the travelling wave and phase shift between the standing wave E- and H-fields are conserved. However, field discontinuity across the mesh discontinuity results thereupon. As a consequence the Poynting vector increases when the wave travels from fine to coarse mesh, and decreases in the opposite case. The Poynting theorem and reciprocity condition are violated. In standard FDTD, these numerical artifacts are at the level of –32 dB for the benchmarking case of ten coarse cells per wavelength and 10:1 mesh grading ratio. The compensated FDTD scheme suppresses the nonphysical effects to the level of −60 dB, which is practically undetectable in FDTD analyses of real problems.
Tracing Sound Objects in Audio Textures

—This contribution presents ﬁrst results on two proposed methods to trace sound objects within texture sounds . We ﬁrst discuss what we mean by these two notions and explain how the properties of a sound that is known to be textural are exploited in order to detect changes which suggest the presence of a distinct sound event. We introduce two approaches, one is based on Gabor multipliers mapping consecutive time-segments of the signal to each other, the other one on dictionary learning. We present the results of simulations based on real data.
Nanosecond semiconductor diodes for pulsed power switching

The development of semiconductor-based nano- and subnanosecond high current breakers is crucial for advancing modern research in experimental physics and radioelectronics, particularly with increasing power (to 1010 W) and repetition rate (to 104 Hz) of impulse devices. Highlighted in this review are two types of silicon diodes: drift step recovery diodes (DSRDs) and SOS diodes with the attainable current densities and switched-off powers being 102 A cm−2 and 108 W in the former case, and 105 A cm−2 and 1010 W in the latter. The possibility of utilizing not only monocrystalline silicon (as in DSRDs and SOS diodes) for the base material but also monocrystalline silicon carbide is examined.
Contraction of rotating magnetized clouds

La contraction d'un nuage interstellaire en rotation, plonge dans un milieu de densite uniforme et traverse par un champ magnetique uniforme est etudiee a l'aide d'un modele simplifie. Le modele du nuage avec une masse subcritique et un noyau en equilibre magnetohydrostatique est construit. La contraction quasi-statique du noyau due a la perte de flux magnetique est ensuite etudiee. L'etape pour laquelle le noyau en quasi-equilibre commence la contraction conservant le moment cinetique est examinee en comparant l'echelle de temps de la perte de moment cinetique avec celle de la contraction. La relation entre les resultats obtenus et les periodes orbitales des binaires est discutee.
Experimental congruence of interval scale production from paired comparisons and ranking for image evaluation

Image evaluation tasks are often conducted using paired comparisons or ranking. To elicit interval scales, both methods rely on Thurstone's Law of Comparative Judgment in which objects closer in psychological space are more often confused in preference comparisons by a putative discriminal random process. It is often debated whether paired comparisons and ranking yield the same interval scales. An experiment was conducted to assess scale production using paired comparisons and ranking. For this experiment a Pioneer Plasma Display and Apple Cinema Display were used for stimulus presentation. Observers performed rank order and paired comparisons tasks on both displays. For each of five scenes, six images were created by manipulating attributes such as lightness, chroma, and hue using six different settings. The intention was to simulate the variability from a set of digital cameras or scanners. Nineteen subjects, (5 females, 14 males) ranging from 19-51 years of age participated in this experiment. Using a paired comparison model and a ranking model, scales were estimated for each display and image combination yielding ten scale pairs, ostensibly measuring the same psychological scale. The Bradley-Terry model was used for the paired comparisons data and the Bradley-Terry-Mallows model was used for the ranking data. Each model was fit using maximum likelihood estimation and assessed using likelihood ratio tests. Approximate 95% confidence intervals were also constructed using likelihood ratios. Model fits for paired comparisons were satisfactory for all scales except those from two image/display pairs; the ranking model fit uniformly well on all data sets. Arguing from overlapping confidence intervals, we conclude that paired comparisons and ranking produce no conflicting decisions regarding ultimate ordering of treatment preferences, but paired comparisons yield greater precision at the expense of lack-of-fit.
Calculation of the Griffith Cohesive Energy of the Ni3AlBx Symmetrical Grain Boundary

A Monte Carlo simulation, with the energetics described by the embedded atom method, has been employed to study the physical behaviour of boron atoms during relaxation of the Ni3AlBinfinity grain boundary. It has also been used to calculate not only the peak concentrations of Ni and B and the valley concentration of Al at the grain boundary, but also the dependence of the grain boundary cohesion on the B bulk concentration. During relaxation of impure Ni3Al grain boundaries, we suggest that, as the segregating species, the B atoms either insert into interstices in the grain boundary or substitute Ni atoms. Meanwhile, as the inducing species, they induce Ni atoms to substitute for Al atoms. Calculations show that in the equilibrium, when the B bulk concentration x increases from 0.1 to 0.9, the peak concentration of B increases, the peak concentration of Ni maximizes while the valley concentration of Al minimizes at x = 0.5. The calculations also show the best cohesion of the grain boundary at x = 0.5.
Studies in astronomical time series analysis. II - Statistical aspects of spectral analysis of unevenly spaced data

Detection of a periodic signal hidden in noise is frequently a goal in astronomical data analysis. This paper does not introduce a new detection technique, but instead studies the reliability and efficiency of detection with the most commonly used technique, the periodogram, in the case where the observation times are unevenly spaced. This choice was made because, of the methods in current use, it appears to have the simplest statistical behavior. A modification of the classical definition of the periodogram is necessary in order to retain the simple statistical behavior of the evenly spaced case. With this modification, periodogram analysis and least-squares fitting of sine waves to the data are exactly equivalent. Certain difficulties with the use of the periodogram are less important than commonly believed in the case of detection of strictly periodic signals. In addition, the standard method for mitigating these difficulties (tapering) can be used just as well if the sampling is uneven. An analysis of the statistical significance of signal detections is presented, with examples
GA and Lyapunov theory-based hybrid adaptive fuzzy controller for non-linear systems

In this present article, a new hybrid methodology for designing stable adaptive fuzzy logic controllers (AFLCs) for a class of non-linear system is proposed. The proposed design strategy exploits the features of genetic algorithm (GA)-based stochastic evolutionary global search technique and Lyapunov theory-based local adaptation scheme. The objective is to develop a methodology for designing AFLCs with optimised free parameters and guaranteed closed-loop stability. Simultaneously, the proposed method introduces automation in the design process. The stand-alone Lyapunov theory-based design, GA-based design and proposed hybrid GA–Lyapunov design methodologies are implemented for two benchmark non-linear plants in simulation case studies with different reference signals and one experimental case study. The results demonstrate that the hybrid design methodology outperforms the other control strategies on the whole.
Evolution of structural and dynamic heterogeneities and activation energy distribution of deformation units in metallic glass

We present experimental results on the distribution and evolution of energy barriers of deformation units in metallic glass (MG) via an activation-relaxation method. Our results show that the dynamical heterogeneity of metallic glass arises from its structural inhomogeneity, and there exist the close correlations between the deformation units, dynamical and structural heterogeneities, and relaxation behaviors in metallic glasses. The results might provide insights on the heterogeneities, plastic deformation, and relaxations behaviors of metallic glass.
Constitutive modeling for moderate deformations of slightly compressible rubber

A constitutive model based on an assumption regarding the general response to hydrostatic pressure is proposed for the moderate deformations of slightly compressible (or nearly incompressible) rubber. It is shown that an excellent fit is obtained with the available experimental data for a particularly simple form of strain-energy density. The data considered are from those material characterization tests that involve only moderate deformations.
Multiproduct production/inventory control under random demands

Studies the optimal production/inventory control policy for a single machine multiproduct production system. The machine produces to fill the end-product inventory stock and the demand is satisfied from the inventory when available; unsatisfied demand is backlogged until the product becomes available as the result of production. For each product, the demand follows a Poisson process and the unit processing time is known. When the machine switches production from one product to another, it incurs a set-up time and a set-up cost. The relevant costs include the set-up cost, a cost per unit time while the machine is running, and linear costs for inventory and backlogging. This problem is modeled as a semi-Markov decision process using the criterion of minimizing expected total cost with discounting over an infinite horizon. Procedures for computing near-optimal policies and their error bounds are developed. The error bound given by the authors' procedure is shown to be much tighter than the one given by the "norm-based" approach. Computational test results are presented to show the structure of the near-optimal policy and how its accuracy is affected by the system characteristics such as capacity utilization and set-up time. >
Mathematical model for volume reverberation: experiment and simulation

An experiment performed in deep water near San Clemente Island, California, showed that discrete scatterers were the primary source of acoustic volume reverberation at the test site. Scatterers reflected the incident waveform without apparent distortion. Estimates of the scatterer density and scatterer reflectivity distribution were obtained from experimental data, but the estimates were distorted by the transducer beam pattern and by overlapping echoes. Analysis of the reverberation envelope showed that reverberation was homogeneous in the horizontal plane and that the reverberation envelope amplitude was not Rayleigh distributed. A computer was programmed to simulate volume reverberation according to a discrete scattering model developed by Faure, Ol'shevskii, and Middleton. The scatterer density and reflectivity estimated from experimental data were changed until simulated and measured reverberation envelopes were statistically alike. When simulated and measured envelopes were alike, improved estimates.
Boundary Integral and Singularity Methods for Linearized Viscous Flow: Index

1. Preliminaries 2. Green's Functions and the Boundary Integral Equation 3. Green's Functions in domains bounded by a solid surface 4. Generalized boundary integral methods 5. Interfacial motion 6. Boundary integral methods based on the Stream Function 7. Discrete representation of a boundary 8. Numerical solution of the integral equations.
Large Eddy Simulations of particle-fluid interaction in a turbulent channel flow

This paper presents a comparison between results obtained using Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) in particle-laden turbulent channel flow. In the case of LES method computations were performed using the dynamic model, Smagorinski model, with and without Van Driest damping at the wall, and without sub-grid scale turbulence modelling. The focus is on the difference in the computed forces acting on a particle in the particle equation of motion. Results for turbulent flow in a channel at Reτ = 150 are presented, focusing on point-particle statistics. DNS provides a point of reference for assessing LES with different sub-filter eddy-viscosity models.
Erratum: Stark-broadening calculations of singly ionized carbon spectral lines

by N. Larbi-Terzi,1‹ S. Sahal-Brechot,2‹ N. Ben Nessib1 and M. S. Dimitrijevic2,3,4 1Groupe de Recherche en Physique Atomique et Astrophysique, Institut National des Sciences Appliquees et de Technologie, University of Carthage, Centre Urbain Nord BP No. 676, 1080 Tunis Cedex, Tunisia 2Laboratoire d’Etude du Rayonnement et de la Matiere en Astrophysique, Observatoire de Paris, UMR CNRS 8112, UPMC, Bâtiment Evry Schatzman, 5 Place Jules Janssen, F-92195 Meudon Cedex, France 3Astronomical Observatory, Volgina 7, 11060 Belgrade 38, Serbia 4Isaac Newton Institute of Chile, Yugoslavia Branch, Volgina 7, 11060 Belgrade, Serbia
InGaN/GaN self-organized quantum dot green light emitting diodes with reduced efficiency droop

High density (2–5×1010 cm−2) self-organized InGaN/GaN quantum dots were grown by plasma-assisted molecular beam epitaxy. Room temperature photoluminescence shows that the quantum dots have strong emission ranging from 430 to 524 nm. The internal quantum efficiency of dots emitting at 500 nm was determined to be 32% by temperature dependent photoluminescence measurements. A recombination lifetime of 0.57 ns is derived from time resolved photoluminescence measurements. These superior optical properties are attributed to a small piezoelectric field in the quantum dots. Light emitting diodes fabricated with the InGaN/GaN quantum dots and emitting at λ=524 nm demonstrate a small blueshift with current injection and reduced efficiency droop.
Impurity seeding for tokamak power exhaust: from present devices via ITER to DEMO

A future fusion reactor is expected to have all-metal plasma facing materials (PFMs) to ensure low erosion rates, low tritium retention and stability against high neutron fluences. As a consequence, intrinsic radiation losses in the plasma edge and divertor are low in comparison to devices with carbon PFMs. To avoid localized overheating in the divertor, intrinsic low-Z and medium-Z impurities have to be inserted into the plasma to convert a major part of the power flux into radiation and to facilitate partial divertor detachment. For burning plasma conditions in ITER, which operates not far above the L–H threshold power, a high divertor radiation level will be mandatory to avoid thermal overload of divertor components. Moreover, in a prototype reactor, DEMO, a high main plasma radiation level will be required in addition for dissipation of the much higher alpha heating power. For divertor plasma conditions in present day tokamaks and in ITER, nitrogen appears most suitable regarding its radiative characteristics. If elevated main chamber radiation is desired as well, argon is the best candidate for the simultaneous enhancement of core and divertor radiation, provided sufficient divertor compression can be obtained. The parameter Psep/R, the power flux through the separatrix normalized by the major radius, is suggested as a suitable scaling (for a given electron density) for the extrapolation of present day divertor conditions to larger devices. The scaling for main chamber radiation from small to large devices has a higher, more favourable dependence of about Prad,main/R2. Krypton provides the smallest fuel dilution for DEMO conditions, but has a more centrally peaked radiation profile compared to argon. For investigation of the different effects of main chamber and divertor radiation and for optimization of their distribution, a double radiative feedback system has been implemented in ASDEX Upgrade (AUG). About half the ITER/DEMO values of Psep/R have been achieved so far, and close to DEMO values of Prad,main/R2, albeit at lower Psep/R. Further increase of this parameter may be achieved by increasing the neutral pressure or improving the divertor geometry.
Modelling of error covariances by 4D‐Var data assimilation

The extended Kalman filter is presented as a good approximation to the optimal assimilation of observations into a numerical weather prediction (NWP) model, as long as the evolution of errors stays close to linear. The error probability distributions are approximated by Gaussians, characterized by their mean and covariance. The full nonlinear forecast model is used to propagate the mean, and a linear model (not necessarily tangent to the full model) the covariances. Since it is impossible to determine the covariances in detail, physically based assumptions about their behaviour must be made; for instance, three‐dimensional balance relationships are used. The linear model can be thought of as extending the covariance relationships to the time dimension. Incremental four‐dimensional variational (4D‐Var) is derived as a practical implementation of the extended Kalman filter, optimally using these modelled covariances for a finite time window. It is easy to include a simplified model of forecast errors in the representation. This Kalman filter based paradigm differs from more traditional derivations of 4D‐Var in attempting to estimate the mean, rather than the mode, of the posterior probability density function. The latter is difficult for a NWP system representing scales which exhibit chaotic behaviour over the period of interest.
Physically constrained maximum likelihood (PCML) mode filtering and its application as a pre-processing method for underwater acoustic communication

Mode filtering is most commonly implemented using the sampled mode shapes or pseudo‐inverse algorithms. [Buck et al. (1998)] placed these techniques in the context of a broader maximum a posteriori (MAP) framework. However, the MAP algorithm requires that the signal and noise statistics be known a priori. Adaptive array processing algorithms are candidates for improving performance without the need for a priori signal and noise statistics. A variant of the physically constrained, maximum‐likelihood (PCML) algorithm [Kraay and Baggeroer (2007)] is developed for mode filtering that achieves the same performance as the MAP mode filter yet does not need a priori knowledge of the signal and noise statistics. The central innovation of this adaptive mode filter is that the received signal’s sample covariance matrix, as estimated by the algorithm, is constrained to be that which can be physically realized given a modal propagation model and an appropriate noise model. Simulation and data processing results from the Shallow Water 2006 experiment are presented along with the application of the mode filter as a broadband pre‐processor for multichannel underwater acoustic communication systems. [This work was supported by ONR through ONR Grant Nos. N00014‐05‐10085 and N00014‐06‐10788. ]