Miracle-dz/UniFAR-FTUs huggingface dataset:
Liquids in porous media

The basic mechanisms which take place during the displacement of immiscible fluids in porous media have been observed in micromodels and have been modelled. At the pore level, in drainage, the invading fluid chooses the largest throat. In imbibition, the displacement depends on the local geometry. For a large pore-to-throat ratio (aspect ratio), the main mechanism is the collapse of the invading fluid in the smallest channel, without entering the pore. For a small aspect ratio, the wetting fluid invades the pore first, and then the adjacent channels. From observations at the pore level, the author has modelled the displacement on a large scale in some extreme cases by using statistical theories. The different behaviours are then displayed as domains in three phase diagrams: one for drainage and two for imbibition (large and small aspect ratios). At a high rate, when viscous forces are dominant, all the diagrams show a stable domain (described by anti-DLA) and a viscous fingering domain (DLA). In drainage, low capillary numbers lead to capillary fingering represented by invasion percolation. In imbibition, the capillary domain is described either by a compact cluster growth (small aspect ratio) or percolation theory (large aspect ratio). In addition the possibility of flow by film along the roughness of the walls leads to disconnected structures.
Methods Based on the Wiener-Hopf Technique for the Solution of Partial Differential Equations

Complex Variable and Fourier Transforms: 1.1 Introduction 1.2 Complex variable theory 1.3 Analytic functions defined by integrals 1.4 The Fourier integral 1.5 The wave equation 1.6 Contour integrals of a certain type 1.7 The Wiener-Hopf procedure Miscellaneous examples and results I Basic Procedures: Half-Plane Problems: 2.1 Introduction 2.2 Jones's method 2.3 A dual integral equation method 2.4 Integral equation formulations 2.5 Solution of the integral equations 2.6 Discussion of the solution 2.7 Comparison of methods 2.8 Boundary conditions specified by general functions 2.9 Radiation-type boundary conditions Miscellaneous examples and results II Further Wave Problems: 3.1 Introduction 3.2 A plane wave incident on two semi-infinite parallel planes 3.3 Radiation from two parallel semi-infinite plates 3.4 Radiation from a cylindrical pipe 3.5 Semi-infinite strips parallel to the walls of a duct 3.6 A strip across a duct Miscellaneous examples and results III Extensions and Limitations of the Method: 4.1 Introduction 4.2 The Hilbert problem 4.3 General considerations 4.4 Simultaneous Wiener-Hopf equations 4.5 Approximate factorization 4.6 Laplace's equation in polar co-ordinates Miscellaneous examples and results IV Some Approximate Methods: 5.1 Introduction 5.2 Some problems which cannot be solved exactly 5.3 General theory of a special equation 5.4 Diffraction by a thick semi-infinite strip 5.5 General theory of another special equation 5.6 Diffraction by strips and slits of finite width Miscellaneous examples and results V The General Solution of the Basic Wiener-Hopf Problem: 6.1 Introduction 6.2 The exact solution of certain dual integral equations Miscellaneous examples and results VI Bibliography Index.
'Interdependent Durations', Second Version

This paper studies the identification of a simultaneous equation model involving duration measures. It proposes a game theoretic model in which durations are determined by strategic agents. In the absence of strategic motives, the model delivers a version of the generalized accelerated failure time model. In its most general form, the system resembles a classical simultaneous equation model in which endogenous variables interact with observable and unobservable exogenous components to characterize a certain economic environment. In this paper, the endogenous variables are the individually chosen equilibrium durations. Even though a unique solution to the game is not always attainable in this context, the structural elements of the economic system are shown to be semiparametrically point identified. We also present a brief discussion of estimation ideas and a set of simulation studies on the model.
Swirling flow of viscoelastic fluids. Part 2. Elastic effects

A torsionally driven cavity has been used to examine the influence of elasticity on the swirling flow of constant-viscosity elastic liquids (Boger fluids). A wealth of phenomena is observed as the degree of inertia, elasticity and viscous forces are varied by using a range of low- to high-viscosity flexible polyacrylamide Boger fluids and a semi-rigid xanthan gum Boger fluid. As the inertia is decreased and elasticity increased by using polyacrylamide Boger fluids, the circulation rates for a ‘Newtonian-like’ secondary flow decreases until flow reversal occurs owing to the increasing magnitude of the primary normal stress difference. For each polyacrylamide fluid, the flow becomes highly unstable at a critical combination of Reynolds number and Weissenberg number resulting in a new time-dependent elastic instability. Each fluid is characterized by a dimensionless elasticity number and a correlation with Reynolds number is found for the occurrence of the instability. In the elasticity dominated flow of the polyacrylamide Boger fluids, the instability disrupts the flow dramatically and causes an increase in the peak axial velocity along the central axis by as much as 400%. In this case, the core vortex spirals with the primary motion of fluid and is observed in some cases at Reynolds numbers much less than unity. Elastic ‘reverse’ flow is observed for the xanthan gum Boger fluid at high Weissenberg number. As the Weissenberg number decreases, and Reynolds number increases, counter-rotating vortices flowing in the inertial direction form on the rotating lid. The peak axial velocity decreases for the xanthan gum Boger fluid with decreasing Weissenberg number. In addition, several constitutive models are used to describe accurately the rheological properties of the fluids used in this work in shear and extensional flow. This experimental investigation of a complex three-dimensional flow using well-characterized fluids provides the information necessary for the validation of non-Newtonian constitutive models through numerical analysis of the torsionally driven cavity flow.
Design of multiplier free linear phase perfect reconstruction filter banks using transformations and genetic algorithms

Perfect reconstruction filter banks and discrete wavelet transforms are finding increasing applications within many image and video processing and coding applications. Due to the high data rates involved in image and video processing, there is a demand for low complexity high performance filter banks. Many of the existing filter bank designs rely on the use of floating point multipliers. These are both expensive to implement, and can lead to rounding errors if they are approximated. This paper considers the design of multiplier free 2-band filter banks, with linear phase and perfect reconstruction properties. The proposed design method also guarantees at least two zeros at the half sampling frequency of the low pass filter, and the zero frequency for the high pass filter.
Pricing European and American bond options under the Hull-White extended Vasicek Model

In this paper, we consider the Hull-White term structure problem with the boundary value condition given as the payoff of a European and American option. We restrict ourselves to the case where parameters of the model are constants and we first derive simple closed–form expression for pricing European bond option in the Hull-White extended Vasicek model framework in term of forward price. The analytic representation of American bond option being very hard to handle, we are forced to resort numerical experiments. We transform the Hull-White term structure equation into the diffusion equation and we first solve it through implicit, explicit and Crank-Nicolson (CN) difference methods. As these finite difference methods require truncation of the domain from infinite to finite one, which may deteriorate the computational efficiency for American bond option, we build a CN method over the unbounded domain. We introduce an exact artificial boundary condition in the pricing boundary value problem to reduce the original problem to an initial boundary problem. Then the CN method is used to solve the reduced problem. The results through illustration show that our method is more efficient and accurate than standard FDMs.
Two-dimensional permittivity and conductivity imaging by full waveform inversion of multioffset GPR data: a frequency-domain quasi-Newton approach

Full waveform inversion of ground-penetrating radar data is an emerging technique for the quantitative, high-resolution imaging of the near subsurface. Here, we present a 2-D frequency-domain full waveform inversion for the simultaneous reconstruction of the dielectric permittivity and of the electrical conductivity. The inverse problem is solved with a quasi-Newton optimization scheme, where the influence of the Hessian is approximated by the L-BFGS-B algorithm. This formulation can be considered to be fully multiparameter since it enables to update permittivity and conductivity values within the same descent step, provided we define scales of measurement through a reference permittivity, a reference conductivity, and an additional scaling factor. Numerical experiments on a benchmark from the literature demonstrate that the inversion is very sensitive to the parameter scaling, despite the consideration of the approximated Hessian that should correct for parameter dimensionalities. A proper scaling should respect the natural sensitivity of the misfit function and give priority to the parameter that has the most impact on the data (the permittivity, in our case). We also investigate the behaviour of the inversion with respect to frequency sampling, considering the selected frequencies either simultaneously or sequentially. As the relative imprint of permittivity and conductivity in the data varies with frequency, the simultaneous reconstruction of both parameters takes a significant benefit from broad frequency bandwidth data, so that simultaneous or cumulative strategies should be favoured. We illustrate our scaling approach with a realistic synthetic example for the imaging of a complex subsurface from on-ground multioffset data. Considering data acquired only from the ground surface increases the ill-posedness of the inverse problem and leads to a strong indetermination of the less-constrained conductivity parameters. A Tikhonov regularization can prevent the creation of high-wavenumber artifacts in the conductivity model that compensate for erroneous low-wavenumber structures, thus enabling to select model solutions. We propose a workflow for multiparameter imaging involving both parameter scaling and regularization. Optimal combinations of scaling factors and regularization weights can be identified by seeking regularization levels that exhibit a clear minimum of final data misfit with respect to parameter scaling. We confirm this workflow by inverting noise-contaminated synthetic data. In a surface-to-surface acquisition configuration, we have been able to reconstruct an accurate permittivity structure and a smooth version of the conductivity distribution, based entirely on the analysis of the data misfit with respect to parameter scaling, for different regularization levels.
Evaluation of binaurally-synchronized dynamic-range compression algorithms for hearing aids

Binaural cues such as interaural level differences (ILD) are used, among other cues, to organize auditory perception and to segregate sound sources in complex acoustical environments. Dynamic-range compression working independently at each ear in a bilateral hearing aid, however, can alter these ILDs, potentially affecting sound source segregation. Binaural synchronization of compression algorithms might thus be necessary to preserve potentially beneficial spatial cues. This study presents a binaurally-linked model-based fast-acting dynamic compression algorithm designed to approximate the normal-hearing basilar membrane input-output function in hearing-impaired listeners. Aim of the evaluation was to assess the effect of binaural synchronization on speech intelligibility and listening effort in spatial masking conditions in comparison to bilateral fitting. Spatially symmetric and asymmetric masking conditions were used. A conventional multiband dynamic compression algorithm both implemented in a bilaterally independent and in a binaurally-linked version, was tested as a reference. Hearing impaired listeners were aided individually with the algorithms for both experiments. Results indicate a small preference towards the modelbased algorithm in challenging masking conditions. However no benefit of binaural-synchronization could be found even for the fast-acting compressor, suggesting a dominant role of the better ear in all experimental conditions. Work funded by BMBF 01EZ0741 and DFG FOR1732
A Linear Stability Analysis of Cavitation in a Finite Blade Count Impeller

The linear stability analysis of cavitation in flat plate cascades corresponding to 2, 3, 4, and 5-bladed impeller was carried out to clarify the effect of the blade count on cavitation instabilities. Each blade is treated independently so that all possible modes in those impellers can be found. In steady flow analysis the alternate blade cavitation was found only for impellers with even number of blades. For 2 or 4-bladed impeller, it was confirmed that there exists no additional destabilizing mode to those found in the previous analysis in which the inter-blade phase difference of disturbance was assumed. It was shown that the modes with total cavity volume fluctuation depend on the inlet duct length while the modes without total cavity volume fluctuation are independent on the system
The Operational Weather Radar Network in Europe

The operational weather radar network in Europe covers more than 30 countries and contains more than 200 weather radars. The radar network is heterogeneous in hardware, signal processing, transmit/receive frequency, and scanning strategy, thus making it fundamentally different than the Next Generation Weather Radar (NEXRAD) network. Another difference is that the density of the European weather radar network is roughly twice that of the NEXRAD network. Within the European National Meteorological Services (EUMETNET), a grouping of services, the Operational Program for Exchange of Weather Radar Information (OPERA) has been working since 1999 on improving the harmonization of radars and their measurements. In addition, OPERA has facilitated and stimulated the exchange of radar data between its members, among others, by the development of a radar data information model and jointly agreed data formats. Since 2011, a radar data center (“Odyssey”) has been in operation, producing network-wide radar mosaics from .
A Curious Example Involving the Likelihood Ratio Test against One-Sided Hypotheses

Abstract An example is presented in which the following curious phenomenon is observed. Let X ∼ N(μ, Ω), where X = (X 1, X 2), μ = (μ1, μ2), Ω11 = Ω22 = 1, and Ω12 = Ω21 = . 90. For a random sample from N(μ, Ω) suppose that the sample mean = (−3, −2); thus every observed value of X 1 and X 2 can be negative. Then, for a suitable hypothesis testing problem with μ1 = 0 being the null hypothesis and being the test statistic, one would accept that μ1 < 0; and similarly, one would accept that μ2 < 0. However, the likelihood ratio test of H 0: μ = 0 against H 1: μ ≥ 0 and μ ≠ 0, would reject H 0 and accept H 1. We do recognize that the hypothesis H 1: μ ≥ 0 and μ ≠ 0 does not allow negative values for μ1 or μ2. Nevertheless, the phenomenon is curious.
Cooperative sensor deployment for multi‐target monitoring

In this paper, the problem of deploying multiple sensor agents (MSAs) to monitor multiple stationary targets is studied. First, the problem is modelled as a special version of the general set‐covering problem. Then a novel motion control scheme is introduced to handle the nonlinear, non‐smooth and non‐additive nature of the multiple objectives that form the cost function in this type of sensor deployment problems. Based on that, a cooperative MSA deployment algorithm is developed. A lower bound for the optimal solution of the set‐covering problem is also derived. Simulation results are presented, demonstrating that given sufficient initial MSA resource, the proposed algorithm is able to lead the MSAs from an arbitrary initial configuration to a final coalition that only requires a near‐minimum number of MSAs to maintain the coverage of the targets. Copyright © 2007 John Wiley & Sons, Ltd.
Splice loss of single-mode fiber as related to fusion time, temperature, and index profile alteration

The lower bound in loss for fusion splices is ∼ 0.01 dB due principally to lateral offset of the cores and alteration of the index profile. This paper investigates the effects on loss of viscous flow and diffusion of the glass constituents during fusion, defining their time-temperature dependencies, and changes in index profile.
Green's function for migration: Continuous recording geometry

Analytical formulas are derived to give the point scatterer responses for the zero‐offset and nonzero‐offset migration operators. These formulas are derived under the far‐field approximation for a continuous distribution of sources and receivers, and are denoted as migration Green’s functions. By specifying a homogeneous velocity model with irregular layers, these Green’s functions can be used to quickly compute the synthetic migrated sections without having to compute the modeled data. Thus, these formulas provide a fundamental understanding of migration artifacts and their relationship to the image point location and source‐receiver configuration. This understanding lays the foundation for the next step, elimination of these artifacts by migration deconvolution.
Determination of fundamental parameters and circumstellar properties for a sample of B[e] stars

Abstract We develop a simple model to derive theoretical continuum energy distributions for B[e] stars, consisting of a B star surrounded by an envelope made of gas and dust. We select a sample of B[e] objects for which we construct the observed energy distributions, from 0.1 to 100 μm, using available photometric and spectroscopic data. We present some preliminary fittings.
AGB star models. Results from 1D stellar evolution and multi-dimensional hydrodynamics simulations

Abstract In this review I am discussing the current state of simulating the internal evolution of AGB stars. Recent work on AGB stars include the effect of rotation, magnetic fields and internal gravity waves, as well as thermohaline mixing induced by the 3He + 3He pp-chain reaction. Hydrodynamic simulations of the interior convection of AGB stars are now becoming available, giving insights to convective boundary mixing, for example for He-shell flash convection. At very low metallicity convective-reactive events are encountered in AGB stars (as well as in massive stars), and the necessity of hydrodynamic simulations to address this difficult phase of stellar evolution is emphasized.
Stimulus‐Oriented Approach to Detection

Distribution curves for amplitude (envelope), drawn for noise and for noise plus signal, provide the basis for determining the proportion of area (probabilities) lying above various “criterion” levels. Probability pairs P (y|n) and P (y|sn) for various criterion levels furnish the coordinates of points generating ROC curves, which, because of the skewness of the distributions, show a slight curvature when plotted on normal‐normal paper. This curvature (concave downward) provides a better fit to detection data obtained from rating‐scale experiments than do the straight lines obtained from normal curves. The ROC curves belong to a family derived through the theory of signal detectability for the ideal observer in the case where signal phase is unspecified. The fact that the distribution for noise‐plus‐signal amplitudes has, in general, a larger variance than that for noise alone explains why many experiments find the ratio of σ sn to σ n to be greater than unity. A detection measure d, derived from the two distribution curves, when plotted against signal amplitude, is a straight line over most of its course but bends in to the origin for weak signals. Its failure to touch the positive abscissa supports the TSD argument against the threshold hypothesis. A second curve, derived from this one, provides a convenient way of determining the signal required to yield a particular value of ds , when the signal that yields some other value of ds is known. Finally, the concept of “effective bandwidth” is developed, and provides a single parameter for use in fitting detection data. Data give some support for the notion that the auditory system adjusts its bandwidth in accordance with the duration of the signal.
Incompressible flow solver of arbitrarily moving bodies with rigid surface

A general procedure of solving incompressible viscous flow around multiple moving bodies was developed. An overlapped unsteady grid system which consists of a stationary main grid and subgrids attached to each moving body was employed. The incompressible N-S equations were calculated over this grid system. As a numerical scheme, the convective terms were approximated by the generalized QUICK method. A semi-implicit second-order two-step method was devised for unsteady time integration. The pressure was accurately solved by the newly developed Neumann Poisson solver. To make the procedure global, a mask function was introduced instead of dividing the main grid into several subregions. Triangular interpolation was applied for data communication between each grid. The accuracy of the procedure was verified by examining the flow around an oscillating cylinder. An application to flows around several moving bodies with multiple overlapped regions was made, which ensured the versatility of the present procedure.
Adaptive Processing of Multilook Complex Sar Images

As the output of the SAR data processor is a complex number, speckle reduction should take profit of the additional information contained in the phase and in the complex correlation between the different images. In order to obtain high equivalent number of looks, we develop the Complex Gaussian-Gamma MAP (Maximum A Posteriori) fdter for complex multiplicative speckle noise and for K-distributed data in the case of L separate correlated complex looks data. This filter is a combination of the usual incoherent multilook processing (Doppler spectral domain) and of an adaptive spatial averaging (image spatial domain). The solution of the filter equation is very easy to handle and is the rigorous solution of the correlated looks MAP fdter.
A posteriori error analysis and adaptive processes in the finite element method: Part II—adaptive mesh refinement

This is a paper presented in two parts dealing respectively with error analysis and adaptive processes applied to finite element calculations. Part I contains the basic theory and methods of deriving error estimates for second-order problems. Part II of the paper deals with the strategy for adaptive refinement and concentrates again on the p-convergent methods. It is shown that an extremely high rate of convergence is reached in practical problems using such procedures. Applications to realistic stress analysis and potential problems are presented.
( 1 × 2 ) Bi chain reconstruction on the InAs(110) surface

The atomic geometry of the $(1\ifmmode\times\else\texttimes\fi{}2)$ Bi reconstruction on the InAs(110) surface has been fully determined by means of grazing incidence x-ray diffraction. The $(1\ifmmode\times\else\texttimes\fi{}2)$ Bi phase is characterized by couples of unequivalent Bi chains bonded alternatively to In and As atoms. The chains are strongly buckled with respect to the (110) InAs plane and they can easily accommodate if the InAs(110) substrate presents alternate missing rows in the [1-10] direction.