Miracle-dz/UniFAR-FTUs huggingface dataset:
Spectral characteristics of turbulence in the hurricane boundary layer over the ocean between the outer rain bands

Spectra and cospectra of wind velocity, potential temperature and humidity have been analysed using data collected in the atmospheric boundary layer in Hurricanes Fabian (2003) and Isabel (2003) during the Coupled Boundary Layer Air– Sea Transfer (CBLAST)—Hurricane experiment. The spectra and cospectra are normalized following the surface layer scaling methods according to similarity theory. It is found that the CBLAST data gathered in the mixed layer between the outer rain bands below 400 m can be grouped into well‐defined curves for spectra of wind velocity, potential temperature and humidity, and for cospectra of momentum and humidity flux. However, the cospectra of sensible heat flux do not exhibit well‐defined universal shape. The CBLAST universal shape spectra and cospectra generally resemble the shapes of those from previous studies, but shift to higher frequencies that correspond to smaller wavelengths of turbulent eddies that contain most of the energy. This work highlights the structural difference between the hurricane boundary layer and the standard atmospheric boundary layer over land and ocean. Copyright © 2010 Royal Meteorological Society
An Ensemble Density-based Clustering Method

Density based clustering is sound for its great ability of finding arbitrary shapes of clusters and identifying the number of clusters automatically. DBSCAN is a frequently used density based clustering algorithm. In DBSCAN a density threshold, which is hard to be chosen adaptively, should be specified to determine whether an object is dense or sparse. In this paper we introduce the concept of clustering ensemble to avoid the difficulty of selecting a single appropriate threshold. Performing DBSCAN multiple times with diverse thresholds picked up from a pre-constructed interval, the final partition can be figured out via a consensus function. Experimental results show that this method can go beyond DBSCAN both in validity and stability, and avoid the inefficiency caused by any inappropriate thresholds.
Thin−film breakdown counter of fission fragments

A new kind of detector of heavy fission fragments is described. The detector is a thin−film capacitor in which electrical breakdowns are nonshorting. The detection is based on the counting of breakdowns which arise when heavy fission fragments hit the capacitor. These breakdowns occur at fields distinctly lower than those due to the application of the field only. The lowering of the breakdown field is discussed considering the thermal or electronic effects for silicon dioxide detectors. The detectors offer immediate information on the magnitude of particle fluxes and may possibly serve to identify the particles.
A new fast algorithm for multiclass hyperspectral image classification with SVM

The support vector machine (SVM) has been a dominant machine-learning technique in the last decade and has demonstrated its efficiency in many applications. Research on classification of hyperspectral images have shown the efficiency of this method to overcome the Hughes phenomenon for classification of such images. A major drawback of classification by SVM is that this classifier was originally developed to solve binary problems, and the algorithms for multiclass problems usually have a high-computational load. In this article, a new and fast method for multiclass problems is proposed. This method has two stages. In the first stage, samples are classified by a maximum likelihood (ML) classifier, and in the second stage, SVM selects the final label of a sample among high-probability classes for that sample by a tree structure. So, for each sample, only some classes must be searched by SVM to find its label. The uncertainty of ML classification for a sample is obtained by the entropy of probabilities, and the number of classes that must be searched by SVM for a sample is obtained based on the uncertainty of that sample in the primary ML classification. This approach is compared with two widely used multiclass algorithms: one-against-one (OAO) and directed acyclic graph (DAGSVM). The obtained results on real data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) revealed less computational time and better accuracy compared to these multiclass algorithms.
Understanding ENSO Diversity

El Nino–Southern Oscillation (ENSO) is a naturally occurring mode of tropical Pacific variability, with global impacts on society and natural ecosystems. While it has long been known that El Nino events display a diverse range of amplitudes, triggers, spatial patterns, and life cycles, the realization that ENSO’s impacts can be highly sensitive to this event-to-event diversity is driving a renewed interest in the subject. This paper surveys our current state of knowledge of ENSO diversity, identifies key gaps in understanding, and outlines some promising future research directions.
Modelling and computation of nonlinear magnetic fields in linear step motors by finite element method

This paper describes the implementation of finite element method (FEM) for modelling and computation of magnetic fields in cylindrical passive armature linear step motors (LSM) used in control rod drives of nuclear reactors. The 2D nonlinear axisymmetric magnetic field is simulated using dedicated finite element (FE) package developed for CAD and performance evaluation of such motors. Various aspects of FE modelling in complex geometry of LSM are discussed. Results are presented in terms of field plots and electromagnetic force versus armature position curves (static characteristics) of the industrial prototype of a LSM. Some of the results are compared with experimental data which show satisfactory agreement. >
Thermodynamics of internal variables in the presence of internal forces

In this paper we have proposed an extension to the current theory of irreversible thermodynamics by introducing the concept of internal force. Within the resulting new framework we show that the phenomenon of creep enhancement, by neutron irradiation, can be explained physically and can be evaluated quantitatively by theoretical means. It is shown that the essential predictions of the theory agree well with experimental observations in the instance cited.
On the Origin of Planetary-Scale Extratropical Winter Circulation Regimes

Abstract Sectorial and planetary-scale winter circulation regimes are studied and the relationship between them is investigated in order to find how much the simultaneous occurrence of sectorial regimes contributes to the occurrence of hemispheric regimes. The strategy is based on the multivariate Gaussian mixture model. The number of components in the model is estimated using two approaches. The first one is based on arguments from order statistics of the mixture proportions and the second uses a more severe test based on reproducibility. The procedure is applied next to the 500-hPa height field over the North Pacific, the North Atlantic, and the Northern Hemisphere using the empirical orthogonal function state space. Two highly significant regimes are found in each case, namely, the Pacific–North America (pattern) (±PNA)–North Atlantic Oscillation (±NAO) for the hemisphere—±PNA for the Pacific sector and ±NAO for the Atlantic sector. The sectorial regimes reflect mainly blocking and no-blocking flows. T.
A short horn with high E-plane directivity

The E -plane beamwidth of a small pyramidal horn can be substantially reduced by the addition of paxabolic cylinder flanges of the proper focal length. Analysis of this antenna involves both geometrical diffraction theory and conventional aperture techniques. In the numerical and experimental examples chosen the flanges halve the half-power beamwidth without severe bandwidth reduction. Consequently a lightweight compact horn is achieved.
Neocortical networks of pyramidal neurons: from local locking and chaos to macroscopic chaos and synchronization

We determine the properties of locking of inhibitory and of excitatory synaptic connections with neocortical pyramidal cells. We are able to give an overview of the emerging periodic behaviour, as a function of the perturbation strength. We show that a chaotic response emerges for inhibitory connections on an open set of positive measure of the parameter space. This implies that synchronization on the set of inhibitory connections is possible, with positive probability.
Dynamics of Flight: Stability and Control

Static Stability and Control General Equations of Unsteady Motion The Stability Derivatives Stability of Uncontrolled Motion Response to Actuation of the Controls-Open Loop Closed-Loop Control Appendices: Analytical Tools Data for Estimating Aerodynamic Derivatives Mean Aerodynamic Chord, Mean Aerodynamic Center, and CMACW Standard Atmosphere and Other Data Data for the Boeing 747-100.
A Generalization of Petterssen's Frontogenesis Function and Its Relation to the Forcing of Vertical Motion

Abstract Petterssen' frontogenesis equation relates the Lagrangian rate of change of the magnitude of the horizontal potential temperature gradient, referred to as the frontogenesis function, to invariant kinematic properties of the horizontal velocity field. It is not uncommon in synoptic practice to infer the presence of vertical circulations in frontal regions from the spatial distribution of the scalar frontogenesis function. On the other hand, Hoskins and collaborators have introduced a form of the quasi-geostrophic omega equation in which the dynamical and forcing is proportional to the horizontal divergence of the so-called Q vector. The Q vector is defined as the Lagrangian rate of change following the geostrophic flow of the vector horizontal potential temperature gradient. The Q-vector formalism motivates us to generalize the Petterssen frontogenesis function to apply to the vector horizontal potential temperature gradient. This generalization, referred to as the vector frontogenesis function, c.
Formation of large-scale structures with sharp density gradient through Rayleigh-Taylor growth in a two-dimensional slab under the two-fluid and finite Larmor radius effects

Two-fluid and the finite Larmor effects on linear and nonlinear growth of the Rayleigh-Taylor instability in a two-dimensional slab are studied numerically with special attention to high-wave-number dynamics and nonlinear structure formation at a low β-value. The two effects stabilize the unstable high wave number modes for a certain range of the β-value. In nonlinear simulations, the absence of the high wave number modes in the linear stage leads to the formation of the density field structure much larger than that in the single-fluid magnetohydrodynamic simulation, together with a sharp density gradient as well as a large velocity difference. The formation of the sharp velocity difference leads to a subsequent Kelvin-Helmholtz-type instability only when both the two-fluid and finite Larmor radius terms are incorporated, whereas it is not observed otherwise. It is shown that the emergence of the secondary instability can modify the outline of the turbulent structures associated with the primary Rayleigh-Taylor instability.
Observation of s‐d exchange force between domain walls and electric current in very thin Permalloy films

Large dc current pulses, ≂2 μs long, are sent through 30–40‐nm‐thick Ni87Fe13 films containing Neel walls. Wall displacements are seen for current densities ≥1.2×107 A/cm2. Displacements reverse when current sense is reversed. Walls always move in direction of charge carriers in this electronlike material. Our results agree with a theory of s‐d exchange interaction between walls and 4s conduction electrons. Hydromagnetic ‘‘domain‐drag’’ forces are too small in such very thin films to explain our data.
Adaptive fuzzy control scheme for MIMO systems with uncertainties

Based on the Lyapunov synthesis approach and regarding the fuzzy systems as approximators to approximate the unknown functions in the system to be controlled, several adaptive fuzzy control schemes have been developed during the last decade. Actually, these schemes have been applied only to simple classes of nonlinear systems. In the concrete, (i) most of them just consider SISO systems (which can avoid the challenging of the coupling between control inputs); (ii) the upper bounds of uncertainties, and the reconstruction errors between the best approximators and their corresponding functions to be approximated are assumed to be known (in this way, the traditional adaptive methods or robust methods could be utilized straightforwardly). This paper develops a design methodology that expends the class of nonlinear systems to MIMO systems, the above restrictive assumptions can be relaxed by using an unique way to deal with the uncertainties and the reconstruction errors. The overall adaptive scheme is shown to guarantee the tracking error, between the outputs of system and the desired values, to be asymptotical in decay.
Inviscid secondary motions in a tube of slowly varying ellipticity

Inviscid methods of treating secondary flows due to streamline curvature are well known in the literature. The development of secondary motions at high Reynolds number in a bifurcation characteristic of the lung airways or the cardiovascular system is considered. In particular, the secondary motions in the initial section of a bifurcation, which can be considered a tube of slowly varying ellipticity, are calculated. Providing viscous effects are confined to regions near the walls, the calculated velocity field agrees with experimental observation. Thus the structure of the secondary motions can be considered an effect of stretching of vortex lines by the tube boundary.
Helium atom in an external electric field: Exact diagonalization

An exact diagonalization method is applied to solve the quantum-mechanical problem of spinless helium atom in an external electric field of arbitrary magnitude. The basis set for two-electron problem is built from different pair combinations ψnalama(αra)ψnblbmb(αrb) of orthonormalized single-particle hydrogen-like wave functions ψnml(r) belonging to any possibly bound states of the individual a- and b-electrons in the Coulomb central field renormalized by the scale parameter α > 0. Within the selected basis the matrix elements of the total Hamiltonian allows an exact analytical representation in the form of finite numerical sums. The diagonalization procedure is performed by Jacobi algorithm for N × N square Hermitian matrix built on the basis of dimension N = 25. The systematics and the numerical values of the low-lying energy levels at zero field are in good agreement with known experimental data. The field dependences of low-lying levels (Stark effect) and polarizability in the ground state of helium a.
Strong and fragile liquids in percolation approach to the glass transition

Liquid- and solid-like particles in a glass are defined via the Lindemann criterion of melting. Due to structure inhomogeneity the amplitude of the mean-square thermal atomic displacements r2 varies spatially. This situation defines a percolation problem for liquid- and solid-like clusters. There are two percolation thresholds: the first corresponds to the temperature T1 at which the first infinite cluster of liquid-like particles appears. The second threshold T2 corresponds to a point at which the last infinite cluster of solid-like particles disappears. In the 3D case T1 ≤ Tg ≤ T2 holds. We argue that this interval is relatively broader in strong glass-formers in comparison with fragile ones; this means that the spatial distribution of r2 and, respectively, of the elastic constants is broader in the former case than in the latter one. Comparison with neutron experimental data on r2 shows that numerically T1 is close to the Vogel-Fulcher-Tammann temperature T0 and T2 is close to the critical temperature Tc defined within mode coupling theory.
The Solar Wind as a Turbulence Laboratory

In this review we will focus on a topic of fundamental importance for both astrophysics and plasma physics, namely the occurrence of large-amplitude low-frequency fluctuations of the fields that describe the plasma state. This subject will be treated within the context of the expanding solar wind and the most meaningful advances in this research field will be reported emphasizing the results obtained in the past decade or so. As a matter of fact, Helios inner heliosphere and Ulysses’ high latitude observations, recent multi-spacecrafts measurements in the solar wind (Cluster four satellites) and new numerical approaches to the problem, based on the dynamics of complex systems, brought new important insights which helped to better understand how turbulent fluctuations behave in the solar wind. In particular, numerical simulations within the realm of magnetohydrodynamic (MHD) turbulence theory unraveled what kind of physical mechanisms are at the basis of turbulence generation and energy transfer across the spectral domain of the fluctuations. In other words, the advances reached in these past years in the investigation of solar wind turbulence now offer a rather complete picture of the phenomenological aspect of the problem to be tentatively presented in a rather organic way.
Dynamical Effects of Global Thermal Instability in Shock-compressed Gas Slabs

We investigate global thermal overstability in the postshock gas flow behind radiative shock waves and its possible role in the fragmentation of shock-compressed gas, by linear perturbation analysis. In order to examine whether the thermal overstability can introduce any characteristic scale length into the fragmentation, we explore the existence of the maximum growth mode with a finite wavelength. We take into account antisymmetric modes of perturbation, as well as symmetric ones, and a cold layer with finite thickness, and we examine a wide range of parameters. The new results of this paper are: (1) there are two kinds of modes, overstable and quasi-oscillatory; (2) unlike previous results, we do not find a dominance of low-order modes over high-overtone ones. We find a scaling relation in dispersion relations of overstable modes, which means that there is no maximum growth mode. We show that the finite thickness of the cold layer only helps make clearer the difference between overstable and quasi-oscillatory modes compared to the zero cold layer thickness cases. We conclude that at least within the linear analysis, the global thermal overstability does not introduce specific length scales to the fragmentation. We present a schematic picture of the driving mechanism of the global thermal instability behind radiative shock waves, and elucidate the difference between the stability properties of radiative and well-studied isothermal shock waves.
Simple improvement method for upper bound of American option

This paper studies the pricing of American options. An upper bound of the price can be made from a martingale and an optimal martingale attains the true price. But it is not easy to find an optimal martingale, and then the improvement of the upper bound is an important problem. In this study, we propose a simple improvement method of the upper bound by stopping times. The stopping times are made from a lower bound process of the continuation value of the American option. We show that a higher lower bound process improves an upper bound more. Finally we show numerically that our method works in the Black–Scholes model.
Grain size effect on the nonlinear dielectric properties of barium titanate ceramics

The nonlinear dielectric properties of dense BaTiO3 ceramics with grain size of 1 μm–90 nm were investigated. In the finest ceramics, the permittivity reduces below 1000 and a remarkable nonhysteretic linear dc-tunability [e(E)] is obtained at high field, above 40 kV/cm. The observed behavior was explained by considering the nanostructured ceramic as a composite formed by ferroelectric grains, whose nonlinearity is reducing, and by low-permittivity nonferroelectric grain boundaries, whose volume fraction increases when decreasing the grain size. Reducing the grain size in ferroelectric dense materials is an alternative route to accomplish the application requirements: nonhysteretic tunability and permittivity below 1000.
Photoinjection into SiO2: Electron Scattering in the Image Force Potential Well

The voltage dependence of photoinjected currents in SiO2 films for electric fields less than about 106 V/cm exhibits anomalous behavior. It is shown that the physical mechanism responsible for this behavior is the scattering of photoinjected electrons in the SiO2 image force potential well between the emitter and the potential maximum. A previously published model attributing the effect to electron trapping in SiO2 is shown to be inconsistent with the experimental results. A theoretical model is presented and the voltage dependence of photocurrents is derived including the effects of scattering and barrier lowering. Experimental results from MIS structures using thermally grown SiO2 are found to be in excellent agreement with theoretical predictions when a 34 A mean free path for scattering in SiO2 is used in the model.
Semi‐global stabilization of discrete‐time systems subject to non‐right invertible constraints

This paper investigates time‐invariant linear systems subject to input and state constraints. We study discrete‐time systems with full or partial constraints on both input and state. It has been shown earlier that the solvability conditions of stabilization problems are closely related to important concepts such as the right invertibility or non‐right invertibility of the constraints, the location of constraint invariant zeros, and the order of constraint infinite zeros. In this paper, for general time‐invariant linear systems with non‐right invertible constraints, necessary and sufficient conditions are developed under which semi‐global stabilization in the admissible set can be achieved by state feedback. Sufficient conditions are also developed for such a stabilization in the case where measurement feedback is used. Such sufficient conditions are almost necessary. Controllers for both state feedback and measurement feedback are constructed as well. Copyright © 2009 John Wiley & Sons, Ltd.
Analysis of the address and sustain discharges in an AC PDP cell using three-dimensional simulation

In the usual two-dimensional (2-D) simulations for the analysis of the plasma discharge in a three-electrodes coplanar-type alternating current plasma display panel (AC PDP) cell, the address electrode is regarded as an infinite plane electrode and the existence of barrier ribs is ignored. We have developed a three-dimensional (3-D) fluid code for the analysis of the plasma discharge in an AC PDP cell, where the address electrode and the barrier ribs can be properly treated. Using this 3-D code, we investigated the dynamics of charged particles and excited species during the address and the sustain periods. Time evolution of the Xe**(/spl ges/6 p states) excited species density profile shows a rounded bright head due to the effect of barrier ribs, which is consistent with the infrared images observed using an image intensified charge coupled device. Sustain voltage ranges for the successful sustenance of display discharges after addressing were obtained using both the 2-D and 3-D simulations through the voltage transfer curve analysis. In addition, the UV luminance and the efficiency changes with the variation of sustain voltages were obtained and compared with those of 2-D simulation.