Miracle-dz/UniFAR-FTUs huggingface dataset:
Eigenvalues, and instabilities of solitary waves

We study a type of ‘eigenvalue’ problem for systems of linear ordinary differential equations with asymptotically constant coefficients by using the analytic function D(λ) introduced by J. W. Evans (1975) in his study of the stability of nerve impulses. We develop a general theory of D(λ) that clarifies the role of the essential spectrum in applications. New formulae for derivatives of D(λ) are used to study linear exponential instabilities of solitary waves for generalizations of: (1) the Korteweg-de Vries equation (KdV); (2) the Benjamin-Bona-Mahoney equation (BBM); and (3) the regularized Boussinesq equation. A pair of real eigenvalues exists, indicating a non-oscillatory instability, when the ‘momentum’ of the wave (a time-invariant functional associated with the hamiltonian structure of the equation) is a decreasing function of wave speed. Also we explain the mechanism of the transition to instability. Unexpectedly, these transitions are unlike typical transitions to instability in finite-dimensional hamiltonian systems. Instead they can be understood in terms of the motion of poles of the resolvent formula extended to a multi-sheeted Riemann surface. Finally, for a generalization of the KdV-Burgers equation (a model for bores), we show that a conjectured transition to instability does not involve real eigenvalues emerging from the origin, suggesting an oscillatory type of instability.
Ultrafast Vibrational Dynamics of Water Disentangled by Reverse Nonequilibrium Ab Initio Molecular Dynamics Simulations

Water is a unique solvent with strong, yet highly dynamic, intermolecular interactions. Many insights into this distinctive liquid have been obtained using ultrafast vibrational spectroscopy of water’s O-H stretch vibration. However, it has been challenging to separate the different contributions to the dynamics of the O-H stretch vibration in H2O. Here, we present a novel nonequilibrium molecular dynamics (NEMD) algorithm that allows for a detailed picture of water vibrational dynamics by generating nonequilibrium vibrationally excited states at targeted vibrational frequencies. Our ab initio NEMD simulations reproduce the experimentally observed time scales of vibrational dynamics in H2O. The approach presented in this work uniquely disentangles the effects on the vibrational dynamics of four contributions: the delocalization of the O-H stretch mode, structural dynamics of the hydrogen bonded network, intramolecular coupling within water molecules, and intermolecular coupling between water molecules (near-resonant energy transfer between O-H groups). Our results illustrate that intermolecular energy transfer and the delocalization of the O-H stretch mode are particularly important for the spectral diffusion in H2O.
COMPARISON OF QUEUES WITH DIFFERENT DISCRETE-TIME ARRIVAL PROCESSES

Traveling times in a FIFO-stochastic event graph are compared in increasing convex ordering for different arrival processes. As a special case, a stochastic lower bound is obtained for the sojourn time in a tandem network of FIFO queues with a Markov arrival process. A counterexample shows that the extended Ross conjecture is not true for discrete-time arrival processes.
Vortex Methods for Direct Numerical Simulation of Three-Dimensional Bluff Body Flows

Recent contributions to the 3-D vortex methods are presented. Following Cottet, the particles strength exchange (PSE) scheme for diffusion is modified in the vicinity of solid boundaries to avoid a spurious vorticity flux and to enforce a zero-normal component of vorticity during the convection/PSE step. The vortex sheet algorithm used to enforce the no-slip boundary condition through a vorticity flux at the boundary and the technique used to perform accurate redistributions in the presence of bodies of general geometry are extended from their 2-D counterpart. To perform simulations with nonuniform resolution, a mapping of the redistribution lattice is used. Computational efficiency is attained through the use of parallel tree codes based on multipole expansions of vortex particles and of vortex panels. The method is validated, by comparisons with other authors' results, on the flow past a sphere at Re=300. It is then applied to compute the flow at Re=500 and 1000.
Moving target detection method based on polarization characteristics under the condition of moving detector

Moving target detection is a important field of image processing. Because the existing algorithms are vulnerable to background disturbance’s interference in the case of moving detector, a moving target detection algorithm based on target’s polarization characteristics under the condition of the moving detector has been proposed in this paper. Firstly, for the problem of the target detection such as the movement of background and parallax which are caused by the moving detector, a moving target detection method under the condition of moving detector has been proposed. The method gets detector’s motion estimation and compensation parameters by using image feature points matching method, and uses background updating method to achieve target’s detection. Then LK optical flow method is used to get target’s movement information and detector’s movement information and model the target’s and background’s movement information. Eventually this method calculates the relevance of the background’s and target’s movement information model to achieve target detection. Secondly, for the moving target detection method could not solve the problem of Background disturbance which interferes the detection result, a target detection method fused target polarization characteristics has been proposed on the basis of moving target detection method under the conditions of the rotation detector. This method realizes the target detection algorithm based on target’s polarization characteristics under the condition of moving detector, by pre-processing the polarization images to solve the parallax’s effect, clustering and segmenting the pretreated polarization image to extract polarized target, and fusing the moving target detection method. The experiment result shows that this method can effectively detect moving targets with a strong polarization characteristics in the scene, while suppressing the interference brought by strong polarized but still region and weak polarized background disturbance in the sense.
Asymptotic properties of imperfect repair models and estimation of repair efficiency

The aim of this articles is to study the asymptotic behavior of two imperfect repair models, called Arithmetic Reduction of Intensity and Arithmetic Reduction of Age models. These models have been proposed by Doyen and Gaudoin (Reliab Eng Syst Safe 84 (2004) 45–56) and include many usual virtual age models. First, it is proved that the failure intensity of these models is asymptotically almost surely equivalent to a deterministic increasing function with a cumulative error proportional to a logarithm. Second, the almost sure convergence and asymptotic normality of several estimators of repair efficiency are derived, when the wear‐out process without repair is known. Finally, the coverage rate of the asymptotic confidence intervals issued from those estimators is empirically studied. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010
Estimating divergence and vorticity from the wind profiler network hourly wind measurements

The large-scale horizontal divergences computed from the kinematic and vorticity methods based on a four-dimensional least squares fit (4-D LSF) to the hourly wind measurements from the Wind Profiler Demonstration Network (WPDN) are compared to the divergence derived from a four-dimensional data assimilation (4-DDA) system. The kinematic method computes divergence by adding the appropriate terms of the velocity derivatives, while the vorticity method uses the dynamical balance of terms in the vorticity equation. The 4-D LSF method produces wind and vorticity analyses by approximating the analyzed wind field as a series of basis functions dependent on both space and time. The sensitivity of the basis functions is studied with an analytic solution and with real data. It is shown that the LSF results are not sensitive to the choice of basis functions as long as they include adequate variation to resolve the data. The high temporal resolution divergence and vorticity fields, which are obtained directly from hourly WPDN data, are used to independently validate the 4-DDA derived vorticity and divergence, which depend both on observational data and on the dynamics and physics in data assimilation models. For the initial case study, the relative errors between the 4-D LSF or the 4-DDA analysis and the WPDN measurements are essentially the same, and the smooth parts of the vorticity derived from these two analyses are similar. The large-scale divergence derived from the vorticity method is also in good agreement with that derived from the 4-DDA analysis. However, the divergence derived from the kinematic method shows little resemblance to those derived from the vorticity method and 4-DDA analysis. DOI: 10.1034/j.1600-0870.1995. 00127.x
Calibration of Limited-Area Ensemble Precipitation Forecasts for Hydrological Predictions

AbstractThe main objective of this study is to investigate the impact of calibration for limited-area ensemble precipitation forecasts, to be used for driving discharge predictions up to 5 days in advance. A reforecast dataset, which spans 30 years, based on the Consortium for Small Scale Modeling Limited-Area Ensemble Prediction System (COSMO-LEPS) was used for testing the calibration strategy. Three calibration techniques were applied: quantile-to-quantile mapping, linear regression, and analogs. The performance of these methodologies was evaluated in terms of statistical scores for the precipitation forecasts operationally provided by COSMO-LEPS in the years 2003–07 over Germany, Switzerland, and the Emilia-Romagna region (northern Italy). The calibration provided a beneficial impact for the ensemble forecast over Switzerland and Germany; whereas, it resulted as less effective for Emilia-Romagna. The analog-based method seemed to be preferred because of its capability of correct position errors and spr.
A Stability Condition for the Numerical Simulation of Poroelastic Systems

In the numerical simulation of the Biot model numerical oscillations may occur if the spatial and discretization parameters are not properly chosen. When the timestep is too small the grid has to be fine enough to resolve the boundary layers that appear in the early stages of the simulation. In this work, we extend a strategy that has been successfully employed in the one-dimensional case for the detection of a critical time-step below which instabilities appear. The idea is to study under which condition the Schur complement of the poroelastic system enjoys a discrete maximum principle property. Differently from the one-dimensional case, in the vectorial case the shear modulus plays a fundamental role for the computation of the Schur complement and the maximum principle argument can be applied only for small shear. We will also investigate the sign of the entries of the Schur complement when the shear and the bulk modulus are of the same magnitude.
THEORETICAL HYDROGEN-LINE RATIOS FOR THE NARROW-LINE REGIONS OF ACTIVE GALACTIC NUCLEI

The authors present calculations of the relative strengths of Lα, Hα, Hβ, Hγ, and Pα for low-density gas clouds photoionized by a continuum such as might be found in active galactic nuclei. They confirm the finding of Halpern (1982) that the Hα/Hβ ratio is insensitive to the ionization parameter. The ratio also depends only weakly on the electron density. Hα/Hβ is mostly a function of metallicity and the shape of the UV to X-ray continuum. It is recommended that Hα/Hβ should be "reinstated" as an indicator of reddening for the narrow-line regions of active galaxies, but with an assumed intrinsic value of about 3.0, as proposed by Halpern, rather than the previous case B value of 2.85.
Measurement of piezoelectric coefficient of gallium nitride using metal-insulator-semiconductor capacitors

Gallium nitride cantilevers with metal-insulator-semiconductor capacitors were fabricated and characterized as a function of strain to determine the effective piezoelectric constant. These cantilevers were tested at room temperature through a combination of cantilever bending experiments, strain gauge measurements, and finite element modeling. By measuring the shift in flatband voltage to applied strain the magnitude of the piezoelectric charge induced is determined. The effective piezoelectric constant e31′ was determined from these measurements to be −0.57±0.03C∕m2.
The Use of Insects as Tracers for “Clear-Air” Boundary-Layer Studies by Doppler Radar

Abstract Single- and multiple-Doppler radar systems are increasingly being used to monitor circulations within the clear-air boundary layer where the scatterers may be gradients of the refractive index or biota or a combination of both. When insects are the primary source of returned radar power, it must be assumed that the insects are either small and are being carried passively in the air, or are flying randomly so that the bulk velocity of all the insects contained within a pulse volume is zero relative to the air. This study presents dual-polarization radar observations of the interaction between a gust flow and a deep cloud of insects within a relatively unstable air mass over North Dakota on 4 July 1987. These data are unique in that they reveal several meteorological conditions for which the preceding assumption is not valid. The boundary layer was not capped, and circulations rose above an apparent threshold altitude above which these insects were not flying. Temperatures near the threshold altitu.
Interstellar matter in early-type galaxies. III - Radio emission and star formation

The relationship between the IR and radio luminosity in early-type galaxies is examined using the correlation among spiral galaxies as a diagnostic of the presence of star formation. For ellipticals, the presence of long-wavelength IR emission enhances the probability that the galaxy is a radio source and is also correlated with the strength of that source. These findings are consistent with the idea that active radio nuclei are due to black holes being fueled by accretion of gas. The majority of S0s detected in both radio and far-IR have a similar ratio of IR to radio luminosity as has been found in spirals, and which is considered to be indicative of recent star formation. Sensitive radio limits for several galaxies reveal another substantial population of S0s with moderately strong IR emission unaccompanied by radio power. 37 references.
Advanced Approach in Sensitive Rule Hiding

Privacy preserving data mining is a novel research direction in data mining and statistical databases, which has recently been proposed in response to the concerns of preserving personal or sensible information derived from data mining algorithms. There have been two types of privacy proposed concerning data mining. The first type of privacy, called output privacy, is that the data is altered so that the mining result will preserve certain privacy. The second type of privacy, called input privacy, is that the data is manipulated so that the mining result is not affected or minimally affected. For output privacy in hiding association rules, current approaches require hidden rules or patterns to be given in advance. However, to specify hidden rules, entire data mining process needs to be executed. For some applications, only certain sensitive rules that contain sensitive items are required to hide. In this work, an algorithm ISSRH (Increase Support Sensitive Rule Hiding) is proposed, to hide the sensitive rules that contain sensitive items, so that sensitive rules containing specified sensitive items on the right hand side of the rule cannot be inferred through association rule mining. Example illustrating the proposed approach is given. The characteristics of the algorithm are discussed.
Multi-view 3D scene reconstruction using ant colony optimization techniques

This paper presents a new method performing high-quality 3D object reconstruction of complex shapes derived from multiple, calibrated photographs of the same scene. The novelty of this research is found in two basic elements, namely: (i) a novel voxel dissimilarity measure, which accommodates the elimination of the lighting variations of the models and (ii) the use of an ant colony approach for further refinement of the final 3D models. The proposed reconstruction procedure employs a volumetric method based on a novel projection test for the production of a visual hull. While the presented algorithm shares certain aspects with the space carving algorithm, it is, nevertheless, first enhanced with the lightness compensating image comparison method, and then refined using ant colony optimization. The algorithm is fast, computationally simple and results in accurate representations of the input scenes. In addition, compared to previous publications, the particular nature of the proposed algorithm allows accurate 3D volumetric measurements under demanding lighting environmental conditions, due to the fact that it can cope with uneven light scenes, resulting from the characteristics of the voxel dissimilarity measure applied. Besides, the intelligent behavior of the ant colony framework provides the opportunity to formulate the process as a combinatorial optimization problem, which can then be solved by means of a colony of cooperating artificial ants, resulting in very promising results. The method is validated with several real datasets, along with qualitative comparisons with other state-of-the-art 3D reconstruction techniques, following the Middlebury benchmark.
Generalized Lyapunov and invariant set theorems for nonlinear dynamical systems

In this paper we develop generalized Lyapunov and invariant set theorems for nonlinear dynamical systems wherein all regularity assumptions on the Lyapunov function and the system dynamics are removed. In particular, local and global stability theorems are given using lower semicontinuous Lyapunov functions. Furthermore, generalized invariant set theorems are derived wherein system trajectories converge to a union of largest invariant sets contained in intersections over finite intervals of the closure of generalized Lyapunov level surfaces. The proposed results provide transparent generalizations to standard Lyapunov and invariant set theorems.
A NEW DIRECTED DIVERGENCE MEASURE AND ITS CHARACTERIZATION

A new information-theoretic divergence measure is introduced and characterized. This new measure is related to the Kullback directed divergence but does not require the condition of absolute continuity to be satisfied by the probability distributions involved. Moreover, both the lower and upper bounds for the new measure are established in terms of the variational distance. A symmetric form of the divergence can also be defined and described by the Shannon entropy function. Other properties of the new divergences: nonnegativity, finiteness, semiboundedness, and boundedness are discussed
Wave Fronts in Wood

A two-dimensional, cylindrically anisotropic, elastic material (infinite in extent) is excited by a point impulsive body force. The non-dimensional elastic constants for the solid obey the relation (α + β) < Γ < (1 + αβ). The characteristic equation which governs the wave front shape is solved exactly in terms of elliptic integrals of the first and third kinds. Initially the wave front, which contains two separate branches, is either smooth and oval shaped (class I) or contains an inner branch carrying four cuspated triangles (class V). As time progresses the wave front distorts as it rotates about the origin. During this time, the cuspated triangles contract in size and finally collapse. Two vanish at time τ ν2 and the remaining two at τ ν1 . When a branch of the wave front encounters the origin it (usually) breaks apart. A circular front (which also satisfies the characteristic equation) must then be adjoined to that wave front branch. The above theory is applied to eleven species of wood.
Roe Matrices for Ideal MHD and Systematic Construction of Roe Matrices for Systems of Conservation Laws

In this paper, the construction of a Roe's scheme for the conservative system of ideal magnetohydrodynamics (MHD) is presented. As this method relies on the computation of a Roe matrix, the problem is to find a matrixA(Ul,Ur) which satisfies the following properties. It is required to be consistent with the jacobian of the fluxF, to have real eigenvalues, a complete set of eigenvectors and to satisfy the relation: ? F=A(Ul,Ur) ? U, whereUlandUrare two admissible states and ? Utheir difference. For the ideal MHD system, using eulerian coordinates, a Roe matrix is obtained without any hypothesis on the specific heat ratio. Especially, its construction relies on an original expression of the magnetic pressure jump. Moreover, a Roe matrix is computed for lagrangian ideal MHD, by extending the results of Munz who obtained such a matrix for the system of lagrangian gas dynamics. So this second matrix involves arithmetic averages unlike the eulerian one, which contains classical Roe averages like in eulerian gas dynamics. In this paper, a systematic construction of lagrangian Roe matrices in terms of eulerian Roe matrices for a general system of conservation laws is also presented. This result, applied to the above eulerian and lagrangian matrices for ideal MHD, gives two new matrices for this system. In the same way, by applying this construction to the gas dynamics equations new Roe matrices are also obtained. All these matrices allow the construction of Roe type schemes. Some numerical examples on the shock tube problem show the applicability of this method.
Further x-ray observations of Hercules X-1 from Uhuru

Recent data are presented concerning the X-ray source Hercules X-1. Details of the 1.24-second pulse shape and its variability are shown. The 1.24- second period is observed to decrease with time, with an overall change of 4.5 mu s between 1972 January and July. The X-ray intensity shows regular on states lasting 11 or 12 days followed by 24-day off states. While ihe source turu-on is not strictly periedic, the shape of the on state can be used to determine a period of 34.88 plus or minus 0.12 days for this cycle. The source turn-ons are found to only occur at one of two well-defined phases in the 1.7-day orbit. In addition to the regular 1.7-day eclipses, regular dips in the X-ray intensity are seen, whose occurrence is related to the orbital phase. These dips are interpreted as absorption by gas in thc system. (auth)
Switching Costs and the Gittins Index

The Theorem of Gittins and Jones (1974) is, perhaps, the single most powerful result in the literature on Bandit problems. This result establishes that in independent-armed Bandit problems with geometric discounting over an infinite horizon, all optimal strategies may be obtained by solving a family of simple optimal stopping problems that associate with each arm an index known as the dynamic allocation index or, more popularly, as the Gittins index. Importantly, the Gittins index of an arm depends solely on the characteristics of that arm and the rate of discounting, and is otherwise completely independent of the problem under consideration. These features simplify significantly the task of characterizing optimal strategies in this class of problems.
High-power single-frequency photonic bandgap fiber amplifier at 1178 nm

1178 nm single-frequency amplification by Yb-doped photonic bandgap fiber has been demonstrated. 24.6 W output was obtained without stimulated Brillouin scattering. 1.8 dB suppression of Brillouin gain by an acoustic antiguiding effect has been found in the low-index core antiresonant reflecting optical waveguide.