Miracle-dz/UniFAR-FTUs huggingface dataset:
Large assemblies of stochastic oscillators

This paper studies the occurrence of stochastic synchronization and phase locking in large assemblies of coupled stochastic oscillators which are modelled as phase-angle stochastic processes. Attention will be restricted to the case of discrete phase-angle spaces. These are technically much simpler than processes over continuous phase spaces and yet show an interesting range of properties. Stochastic synchronization occurs if the oscillator assembly obeys a large deviation principle and if the deterministic-limit dynamics possesses a stable periodic orbit. All relevant concepts are reviewed in §§ 1, 2 and the Appendix. In §4, general necessary and sufficient conditions for stochastic synchronization are obtained. Weak and robust types of synchronization are distinguished. A describing function method is formulated which is very convenient for checking the general conditions in concrete examples. Separate treatments of feedback gain, feedback type (i.e. positive or negative) and feedback sources lead to investigations of how the occurrence of stochastic synchronization depends on any one of those feedback aspects. In a sequence of gradually more realistic models (§§ 3, 4b,5a), the general results are applied to assemblies of (stochastic) fireflies. The first of these models (§ 3) is mathematically instructive in that it provides a good example of how the Liapunov-function character of large deviation rate functions can be exploited to study global properties of the corresponding deterministic limit ode. The analysis of firefly assemblies culminates in a proof of stochastic firefly synchronization. This result is the precise stochastic analogue of the well-known proof of deterministic firefly synchronization given by Mirollo & Strogatz (1990). In § 5, the general results of § 4 are applied to neuronal assemblies. Particular attention is paid to the dependence of neuronal synchronization on the feedback type, that is excitatory or inhibitory signalling. We find it natural and instructive to distinguish between external and internal variants of inhibition. The latter (in particular, in the form of graded refractoriness of neurons) is shown to be crucial for stochastic synchronization within one neural assembly, whereas the former is instrumental for phase locking between distinct assemblies. These findings are summarized and sharpened in a number of concrete predictions for real biological networks of neurons. Except for some topical aspects of large deviation theory (reviewed in the Appendix), the mathematics employed in this paper are straightforward.
Light collection in scintillation detector composites for neutron detection

The authors have been investigating the heterogeneous combination of neutron-conversion materials in a plastic or liquid scintillation matrix with the goal of developing neutron detectors of high detection efficiency and fast response. They report on one such combination, consisting of thin-wall glass microspheres filled with high-pressure /sup 3/He gas dispersed in plastic scintillation. They have developed glass formulations that are capable of containing the helium in shells with wall thickness as low as 1 mu m with leak rates at room temperature that correspond to several years half life. The energy loss of the reaction products in the shell wall and the low light yield of plastic scintillations for low-energy protons result in low light yield per event. The authors discuss the use of an optical modeling code to investigate the incorporation of wavelength-shifting elements to aid in the collection of this light from highly scattering composite scintillation media. >
Reflection Z-scan technique for the study of nonlinear refraction and absorption of a single interface and thin film

Spatial modification of a Gaussian beam reflected from a single interface and a thin film with intensity-dependent refractive index and absorption coefficient is studied theoretically. The measurement of this modification by different positions of the nonlinear surface with respect to the beam waist (the modified Z-scan technique) can be used to study nonlinear optical properties. For a single interface the measurements permit the nonlinear parameters to be determined unambiguously. For a thin film the multiple internal reflections are important, and the value and the sign of nonlinear refraction and absorption coefficients cannot be uniquely found.
A Dynamic Hard Sphere Model

A simple two‐dimensional model, in which uniform hard spheres are made to move steadily and apparently nearly at random, is described. At low sphere density the model exhibits ``gas‐like'' behavior. As the density is increased the behavior becomes more ``liquid‐like'' and then ``crystallization'' occurs. Many dynamic atomic phenomena, believed to occur in the gas, liquid, or solid state, are illustrated by the model.
Application of Artificial Neural Network Forecasts to Predict Fog at Canberra International Airport

Abstract The occurrence of fog can significantly impact air transport operations, and plays an important role in aviation safety. The economic value of aviation forecasts for Sydney Airport alone in 1993 was estimated at $6.8 million (Australian dollars) for Quantas Airways. The prediction of fog remains difficult despite improvements in numerical weather prediction guidance and models of the fog phenomenon. This paper assesses the ability of artificial neural networks (ANNs) to provide accurate forecasts of such events at Canberra International Airport (YSCB). Unlike conventional statistical techniques, ANNs are well suited to problems involving complex nonlinear interactions and therefore have potential in application to fog prediction. A 44-yr database of standard meteorological observations obtained from the Australian Bureau of Meteorology was used to develop, train, test, and validate ANNs designed to predict fog occurrence. Fog forecasting aids were developed for 3-, 6-, 12-, and 18-h lead times fr.
Radio and X-Ray Studies of a Coronal Mass Ejection Associated with a Very Slow Prominence Eruption

We report on the observations of an X-ray coronal mass ejection (CME) with its three part structure: frontal loop, coronal cavity, and the eruptive prominence core. The prominence core was observed in microwaves, and the frontal loop was observed in X-rays. A coronal volume much larger than that occupied by the prominence seems to be affected by the eruption. Formation of an arcade structure was also observed beneath the erupting prominence. X-ray enhancement at the arcade persisted for several hours similar to long decay events. At the apex of the arcade there was a bright knot, which we interpret as the reconnection region from which the filament gets detached. We determined the trajectories of the frontal loop and the prominence core and found them to have very different characteristics. The CME showed an extremely small acceleration, while the prominence had a linear motion in the beginning followed by an exponential rise. However, during the several hours of simultaneous observation, the prominence did not catch up with the frontal loop. We determined the evolution of the CME mass, which increased by a factor of 4 during our observations. We discuss the implications of the observations in the general context of coronal mass ejections.
SIMULTANEOUS SPECTROSCOPIC AND PHOTOMETRIC OBSERVATIONS OF FOUR T TAURI-TYPE VARIABLES.

Simultaneous spectroscopic and photometric observations of the T Tauri-type variables CW Tau, DF Tau, DG Tau,and DR Tau are presented. Most of the light variability can be interpreted as the result of changes in the intensity of a source of continous emission located somewhere in the system. However, a few of the light variations in DF Tau and DR Tau may result from changes in circumstellar opacity, while differences in the variation with luminosity of the emission-line strengths of certain ions in CW Tau and DF Tau indicate that changes in continuum emission are not the entire explanation of the observed variability in these two systems. Comparison with other investigations suggests that, at times, the light variations in all four of these stars result from the occurrence of other types of phenomena than those observed in the present study. The present observations emphasize the fact that the phenomena associated with the T Tau phase of stellar evolution are complex and differ from star to star.
Computational Fluid Dynamics Study of Liquid Droplet Impingement Erosion in the Inner Wall of a Bent Pipe

The bent pipe wall thinning phenomenon has been often found at the elbow of pipelines in the power engineering industry. Liquid droplet impingement (LDI) erosion could be regarded to be one of the major causes of unexpected troubles occasionally occurred in the inner bent pipe surface. In this paper, three-dimensional numerical simulations are conducted for a bent pipe. Typically the pipe diameter is 170mm and the bending angle is 90 degree, the mass flow rate of droplet is 4.5×10-3 kg/s with the velocity of 280m/s at the entry. The calculations employ a two-phase flow model. A computational fluid dynamic tool has been adopted by using one-way and two-way fluid-droplet coupled system in high Reynolds number regions. This computational fluid model is built up by incompressible Reynolds averaged Navier-Stokes equations using different turbulent flow computational models and the SIMPLE algorithm, and the numerical droplet model adopts the Lagrangian approach. The momentum transfers between droplet and carrier fluid are calculated by using two different fluid-droplet coupled methods. The interactional force between carrier and droplet are taken into account by momentum transfer in Eulerian-Lagrangian approaches. Based on the carrier streamlines and droplet trajectories, the two-way calculation using the interactional momentum transfer calculations could be a more appropriate model to simulate the bent pipe wall thinning phenomena, the effects of droplet size are also demonstrated numerically. Finally, it is shown that turbulence models are not sensitive to the involved droplets.
Numerical Guidance Methods for Decision Support in Aviation Meteorological Forecasting

Abstract Numerical guidance methods for decision making support of aviation meteorological forecasters are presented. The methods have been developed to enhance the usefulness of numerical weather prediction (NWP) model data and local and upstream observations in the production of terminal aerodrome forecasts (TAFs) and trend-type forecasts (TRENDs) for airports. In this paper two newly developed methods are described and it is shown how they are used to derive numerical guidance products for aviation. The first is a combination of statistical and physical postprocessing of NWP model data and in situ observations. This method is used to derive forecasts for all aviation-related meteorological parameters at the airport. The second is a high-resolution wind transformation method, a technique used to derive local wind at airports from grid-box-averaged NWP model winds. For operational use of the numerical guidance products encoding software is provided for automatic production of an alphanumeric TAF and TREN.
Adaptive coding and prediction of sources with large and infinite alphabets

The problem of predicting a sequence generated by a discrete source with unknown statistics is considered. This problem is of great importance for data compression, because of its use to estimate probability distributions for PPM algorithms and other adaptive codes. This paper suggested a scheme of adaptive coding (and prediction) for a case where a source generates letters from an alphabet with unknown or infinite size. This scheme can be applied along with Laplace, Krichevsky and any other predictors. The general case of the prediction, which is based on such a grouping, is considered and the estimates of the redundancy are given.
Interpretation of the gas flow field modification induced by guided streamer (‘plasma bullet’) propagation

Atmospheric-pressure non-equilibrium plasmas of noble gases in the form of ‘bullets’ have attracted considerable attention, against cold low-pressure or thermal atmospheric-pressure plasmas, for multidisciplinary scientific fields such as material science and biomedicine, due to their unique compatible features. A key factor for the efficiency of most of these systems is the interaction between the noble-gas channel, where the ‘bullets’ (streamers) propagate, and the plasma itself. It is the object of this paper to demonstrate this interaction and to provide the explanation on the gas flow field modification induced by the plasma ignition. A three-dimensional numerical model incorporating most of the governing equations, schlieren imaging and UV–visible high-resolution optical emission spectroscopy are applied. In accordance with the present results, the mechanism leading to the flow field alteration is clearly related to the electrohydrodynamic force, while it is demonstrated that the gas temperature plays a minor role.
Dynamic Image-Based Visual Servo Control For An Aerial Robot: Theory and Experiments

This article considers the question of dynamic image-based visual servo control for a vertical take-off and landing unmanned aerial vehicle. The visual targets considered are colored blobs on a flat surface to which the normal direction is known. A fully nonlinear adaptive control design coupled with an asymptotic filter is provided that ensures the stability of the closed-loop system in a large domain. The image features used are a modified first order spherical moment for position regulation and optic flow for velocity damping.
Guiding-center simulations of nonlocal and negative inertia effects on rotation in a tokamak

The magnitude of the radial electric field (Er), resulting from nonambipolar fluxes of neoclassical origin, is evaluated using Monte Carlo guiding-center simulations for a low-current plasma corresponding to the FT-2 tokamak {Fisichiskii Tokamak-2, Ioffe Institute, St. Petersburg [S. I. Lashkul, V. N. Budnikov, E. O. Vekshina et al., Plasma Phys. Rep. 27, 1001 (2001)]}. The Er-values are found to significantly exceed those given by the standard neoclassical theory, based on thin-orbit assumption, when the plasma current is sufficiently low and the pressure gradient is sufficiently high. Strong Er-structures are found to form in the same low plasma-current range where enhanced confinement is reported in the FT-2 tokamak. In the simulations, the physics behind the strong increase in the field values is intimately related to the poloidal Mach-number, together with the wide ion orbits.
Infrared Spectroscopy of Blue Dwarf Galaxies

We present a survey of the near-infrared emission lines of eight blue dwarf galaxies. These galaxies have advantages for study of the excitation of the interstellar medium by starbursts because the effects are relatively undiluted by the quiescent stellar population, the star formation episodes usually appear to be of short duration, and the effects of metallicity can be examined. Diagnostic tools for the interpretation of [Fe II](1.64) and H2(2.12) emission lines emitted by starburst galaxies are developed and the results are compared with a starburst model. We confirm that the [Fe II](1.64) line is mainly excited in supernova remnants, but the H2 emission appears to arise from a variety of different excitation mechanisms. Many of the galaxies show evidence for a fluorescently excited component of H2. The temperature of the hot stellar population is analyzed by means of the He I(1.70 μm) emission line and compared with estimates from the [O III]/Hβ ratio in the optical and from the mid-infrared fine structure lines. The agreement is reasonably good, although there appears to be a tendency for the temperature to be overestimated by use of the [O III]/Hβ ratio.
Toward Efficient Computation of Compressible and Incompressible Flows

The combination of explicit Runge-Kutta time integration with the solution of an implicit system of equations, which in earlier work demonstrated increased efficiency in computing compressible flow on highly stretched meshes, is extended toward conditions where the free stream Mach number approaches zero. Expressing the inviscid flux Jacobians in terms of Mach number, an artificial speed of sound as in low Mach number preconditioning is introduced into the Jacobians, leading to a consistent formulation of the implicit and explicit parts of the discrete equations. Besides extension to low Mach number flows, the proposed method allowed increasing the admissible CFL number from O(100) to O(1000). The implicit step introduced into the Runge-Kutta scheme serves as a preconditioner which addresses both, the stiffness in the discrete equations associated with highly stretched meshes, and the stiffness in the analytical equations associated with the disparity in the eigenvalues of the inviscid flux Jacobians. Integrated into the framework of a multigrid algorithm, the method is applied to efficiently compute different cases of inviscid flow around airfoils at various Mach numbers, and viscous turbulent airfoil flow with varying Mach and Reynolds number. Compared to well tuned conventional methods, computation times are reduced by half an order of magnitude
A phenomenological theory of rotating turbulence

We present direct numerical simulations of statistically homogeneous, freely decaying, rotating turbulence in which the Rossby number, Ro = u⊥/2Ωl⊥, is of order unity. This is the regime normally encountered in laboratory experiments. The initial condition consists of fully developed turbulence in which Ro is sufficiently high for rotational effects to be weak. However, as the kinetic energy falls, so also does Ro, and quite quickly, we enter a regime in which the Coriolis force is relatively strong and anisotropy grows rapidly, with l⊥ ≪ l∥. This regime occurs when Ro ∼ 0.4 and is characterised by an almost constant perpendicular integral scale, l⊥ ∼ constant, a rapid linear growth in the integral scale parallel to the rotation axis, l∥ ∼ l⊥Ωt, and a slow decline in the value of Ro. We observe that the rate of dissipation of energy scales as e ∼ u3/l∥ and that both the perpendicular and parallel energy spectra exhibit a k−5/3 inertial range; Ek⊥∼e2/3k⊥−5/3 and Ek∥∼e2/3k∥−5/3. We show that these power-law.
Limits of Singularly Perturbed Control Problems with Statistical Dynamics of Fast Motions

We describe the limit behavior of admissible trajectories in a singularly perturbed control system as the small parameter tends to zero. A general case is considered where, in the limit, the fast motion may infinitely rapidly oscillate in time. Invariant measures of the parameterized fast flow are employed to describe the limit behavior and construct the limit control problem. The notion of relatively slow controls is introduced. Approximating properties of the limit problem within the families of relatively slow controls are verified. The results are illustrated by examples.
Computational modeling of process induced damage during plasma clean

When partially completed circuits come in contact with plasmas during integrated circuit fabrication, current from the plasma can potentially damage active devices on the wafer. A suite of computational models is used in this article to investigate damage to ultrathin (1.0–5.5nm) transistor gate dielectric (SiO2) during Ar∕O2 based plasma cleaning in a capacitively coupled plasma reactor. This modeling infrastructure includes a two-dimensional plasma equipment model for relating process control parameters to ion and electron currents, a three-dimensional model for flux density calculation within a circular via, an electrostatic model for computing potential across the gate dielectric, and a percolation model to investigate dielectric damage characteristics. Computational results show that when the plasma current comes in contact with the gate dielectric, the gate dielectric rapidly charges up and the potential difference across the dielectric saturates at the level necessary to support the plasma induced .
Extended Huckel tight-binding calculations of the electronic structure of YbFe 4 Sb 12 , UFe 4 P 12 , and ThFe 4 P 12

Calculation of the band structure, total and projected density of states, crystal orbital population analysis (COOP), and Mulliken population analysis were performed for the filled skutterudites YbFe 4 Sb 1 2 , UFe 4 P 1 2 , and ThFe 4 P 1 2 . The calculated energy bands depict a semimetal behavior for YbFe 4 Sb 1 2 and UFe 4 P 1 2 , and metallic behavior for ThFe 4 P 1 2 . Furthermore, the contributions from each orbital to the total DOS for each compound corroborate these findings. The bonding strength was derived from the COOP analysis between different pairs of atoms, considering nearest neighbor distances between 3.40 and 6.47 A for YbFe 4 Sb 1 2 , 2.91 and 6.47 A for UFe 4 P 1 2 , and 2.48 and 5.51 A for ThFe 4 P 1 2 . Mulliken population analysis suggests ionic behavior for these compounds.
ON THE LYAPUNOV APPROACH TO ROBUST STABILIZATION OF UNCERTAIN NONLINEAR SYSTEMS

In the Lyapunov approach employed in this paper, known in the literature as Lyapunov control, or min-max control, robust, global uniform asymptotic stability is achieved by a discontinuous control law which ensures that the Lyapunov derivative is negative despite bounded uncertainty. For that, it is assumed that the uncertainties satisfy certain matching conditions, and that a Lyapunov function for the nominal plant is available. To obtain lower control magnitudes, this paper develops control laws which counter the uncertainties on a component-wise basis, rather than the usual normic one. Both the basic discontinuous control law, which is proved to provide robust global uniform asymptotic stability, and a continuous app roximation, which is proved to ensure global uniform ultimate boundedness, are derived. Application to model following is given. We adapt recent results on robust quadratic stabilization of nominally linear time-invariant plants subjected to nonlinear, bo unded and unmatched uncertain perturbations, to extend our results to this important class of systems; this is illustrated by two examples.
Resonance Surfaces in the Ion Cyclotron Frequency Range in Toroidal Systems

Resonance surfaces are investigated in a toroidal geometry for waves in the ion cyclotron frequency regime. In this geometry stationary waves are described by partial differential equations. Three kinds of resonances appear in this regime of a multicomponent plasma, the fundamental ion cyclotron resonance, the perpendicular ion cyclotron resonance, and Buchsbaum's ion-ion hybrid resonance. In a two-dimensional axially symmetric plasma the last two resonances can be obtained by solving ordinary differential equations. The perpendicular ion cyclotron resonance coincides with a magnetic surface, while the ion-ion hybrid resonance in general makes a small angle of the order of meB/miBP with the magnetic surfaces, except close to the fundamental cyclotron resonances, where the angle becomes large.
A Novel PA Behavioral Modeling Using Memory Rational Function

Aiming at the nonlinear characteristics and memory effects of power amplifier, a memory rational function behavioral model, which based on the memory polynomial model and memoryless rational function model, is proposed. The model coefficients are identified by conjugate gradient method. The estimation of the best model nonlinearity order and the best memory depth is carried out by minimized the normalized mean squared error (MNSE). The model is validated using multi-carrier WCDMA signal and a MRF6S21140H power amplifier by measurement. The result indicates that the proposed model can achieve better model performance with less number of coefficients compared to the memory polynomial model and memoryless rational function model