Miracle-dz/UniFAR-FTUs huggingface dataset:
Regularized maximum likelihood estimate for infinite dimensional parameter in stochastic parabolic systems

A previous study by S.I. Aihara and Y. Sunahara (SIAM J. Control Optim., vol.26, p.1062-75, 1988), in which necessary conditions for the maximum likelihood estimation (MLE) of an infinite dimensional parameter for stochastic parabolic systems were derived, is continued. An algorithm for seeking one of solutions that satisfy the necessary conditions with the aid of a regularization technique is constructed. <<ETX>>
On Extremal Solutions of Controlled Nonlinear Filtering Equations

Controlled nonlinear filtering equations with "relaxed controls" arising out of the separated control problem for partially observed diffusions are considered. An equivalence relation is defined on the attainable laws of the joint state and control process by identifying any two of the latter when their one-dimensional marginals agree almost everywhere. Extreme points of the set of such equivalence classes (for fixed initial laws) are shown to correspond to Markov processes.
Practical Theory of the Multilayered Transition Radiation Detector

The transition radiation detector for ultrarelativistic particles with a multifoil radiator is studied in the following aspects: x-ray spectrum, $\ensuremath{\gamma}$ dependence, interference effects, saturation at high $\ensuremath{\gamma}$, effects of irregularities, and multiple scattering. The analysis is simplified by reducing the various parameters to essentially three dimensionless quantities: a scaled Lorentz factor $\ensuremath{\Gamma}$, a scaled frequency $\ensuremath{\nu}$, and the ratio $\ensuremath{\tau}=\frac{\mathrm{foil} \mathrm{spacing}}{\mathrm{foil} \mathrm{thickness}}$. Large threshold effects due to interference are predicted which can be used to build a threshold detector or to measure the x-ray index of refraction of a material. Theoretical curves are given. Photon statistics, optimization of the detector, and computational method are discussed briefly.
Diffraction analysis of three-dimensional volume gratings with arbitrary boundaries

On the basis of two-dimensional coupled-wave theory, the diffraction of finite bounded beams with arbitrary profiles by nonuniform, arbitrarily bounded mixed volume gratings is described, taking into account deviations from the Bragg condition, attenuation of the modulation depth, and constant absorption. The resulting differential equations are solved numerically with a two-dimensional Runge–Kutta method. The quality of the diffracted beam is influenced strongly by the deviation from the Bragg case. Planar finite gratings in contrast to crossed-beam gratings, show a smoothing effect of the diffraction characteristics. This is also found for crossed-beam gratings with a moderate attenuation. It is demonstrated that the amplitude profiles of the grating writing beams and the readout beams have a strong influence on the intensity profiles of the diffracted beams.
Information from the Kinematics of F and G Stars in the Solar Neighborhood

We have calculated the orbital parameters for 90 stars in Chen et al. and updated the kinematic data for stars in Edvardsson et al. by using the accurate Hipparcos parallaxes and proper motions, and recalculated the -element abundances in Edvardsson et al. in a way consistent with Chen et al. The two sets of data are combined in a study of stellar populations and characteristics of F & G stars in the solar neighborhood. We confirm the result of Chen et al. that a distinguishable group of stars may belong to the thick disk rather than the thin disk. The ages for the stars are determined using the theoretical isochrones of VandenBerg et al. The age-metallicity relation is investigated for dierent subgroups according to distance from the sun and galactic orbital parameters. It is found that a mixing of stars with dierent orbital parameters significantly aect the age-metallicity relation for the disk. Stars with orbits confined to the solar circle all have metallicities (Fe/H) > 0.3 irrespective of their distances from the sun or from the Galactic plane.
Imaging polarimetry of class I young stellar objects

We present near-infrared imaging polarimetry of three class I young stellar objects in the Taurus–Auriga dark cloud. We use Monte Carlo simulations to analyse the flux distributions and polarization patterns of these three sources and five others from an earlier paper. In addition, we present high-resolution polarimetry of HL Tau using the shift and add technique. Most young stellar objects in the sample display sharp, unresolved, peaks in the scattered light distribution. This is most simply explained by a strong concentration of matter in the centre, which we model by applying the ρ ∝ r−1.5 power law throughout the envelope. In terms of the Ulrich/Terebey, Shu and Cassen solution for the late stages of contraction of an initially spherical non-magnetic cloud, this corresponds to rc < 10 au. However, this almost spherically symmetric density distribution is inconsistent with observations of flattened, disc-like structures, so we conclude that this solution is not appropriate and different initial conditions apply. The multiple-scattering models with spherical grains do not reproduce some features of the observed polarization patterns, in particular the broad regions of aligned vectors seen in some sources. We interpret this as evidence for elongated aligned grains. The weak wavelength dependence of nebular morphology shows that the dust grains in circumstellar envelopes obey a much shallower extinction law than interstellar grains in the near-infrared, which we describe by the opacity ratio κ(J/K) = 1.8 ± 0.3, compared to the interstellar value of 3.25. We place an upper limit on albedo of ω < 0.6 from 1.25 to 2.2 μm and we find 0.1 < ω < 0.6 at 2.2 μm. Analysis of the quadrupolar source IRAS 04302+2247 indicates that the scattering function is not highly forward-throwing, which we express by the constraint g = 〈 cos(τ) 〉 < 0.4. With the addition of two more observables derived from the observed degrees of linear and circular polarization, we identify five empirical constraints on the properties of circumstellar dust. After calculating these observables for grain mixtures with a wide range of refractive indices and a variety of size distributions, we find that highly metallic spherical grains or highly elongated grains can satisfy these constraints and the size distribution extends to a a 0.35 μm. Amorphous carbon is the most plausible absorptive component, since graphite appears to be ruled out by its strong dispersion in the near-infrared.
A higher‐order unsplit 2D direct Eulerian finite volume method for two‐material compressible flows based on the MOOD paradigms

A higher‐order unsplit multi‐dimensional discretization of the diffuse interface model for two‐material compressible flows proposed by R. Saurel, F. Petitpas and R. A. Berry in 2009 is developed. The proposed higher‐order method is based on the concepts of the Multidimensional Optimal Order Detection (MOOD) method introduced in three recent papers for single‐material flows. The first‐order unsplit multi‐dimensional Finite Volume discretization presented by SPB serves as foundation for the development of the higher‐order unlimited schemes. Specific detection criteria along with a novel decrementing algorithm for the MOOD method are designed in order to deal with the complexity of multi‐material flows. Numerically, we compare errors and computational times on several 1D problems (stringent shock tube and cavitation problems) computed on 2D meshes with the second‐ and fourth‐order MOOD methods using a classical MUSCL method as reference. Several simulations of a 2D shocked R22 bubble in the air are also presented on Cartesian and unstructured meshes with the second‐ and fourth‐order MOOD methods, and qualitative comparisons confirm the conclusions obtained with 1D problems. These numerical results demonstrate the robustness of the MOOD approach and the interest of using more than second‐order methods even for locally singular solutions of complex physics models. Copyright © 2014 John Wiley & Sons, Ltd.
Phase-correction algorithm of deformed grating images in the depth measurement of weld pool surface in gas tungsten arc welding

The principle and system structure of the depth measurement of weld pool surface in tungsten insert gas (TIG) welding are first introduced in the paper, then the problem of the common phase lines is studied. We analyze the causes and characteristics of the phase lines, and propose a phase correction method based on line ratio. The paper presents the principle and detail processing steps of this phase correction algorithm, and then the effectiveness and processing characteristics of the algorithm are verified by simulation. Finally, the algorithm is applied to phase processing in the depth measurement of the TIG weld pool surface and obtains satisfying results.
Modal projections for synchronous rotor whirl

We consider the synchronous whirl of arbitrary axisymmetric rotors supported on rigid bearings. Prior computational treatments of this problem were based on adding element-level gyroscopic terms to the governing equations. Here, we begin with a direct continuum formulation wherein gyroscopic terms need not be added on separately and explicitly: all gyroscopic effects are captured implicitly within the continuum elastodynamics. We present two new methods for obtaining the whirl speed, where we project the dynamic equilibrium equations of the rotor on to a few of its non-spinning vibration mode shapes. The first modal projection method is direct and more accurate, but requires numerical evaluation of more demanding integrals. The second method is iterative and involves a small approximation, but is simpler. Both the methods are based on one new insight: the gyroscopic terms used in other treatments are essentially the result of a prestress in the rotor caused by the non-zero spin rate, and may be incorporated as such in the continuum formulation. The accuracy of the results obtained, for several examples, is verified against detailed calculations with a commercial finite-element package, against our own nonlinear finite-element code or against analytical estimates. For further verification and illustration, a closed-form analytical solution for a simple problem, obtained using our method, matches the results obtained with explicit gyroscopic terms.
The Impact of Supplemental Dropwindsonde Data on the Structure and Intensity of Tropical Storm Karen (2013) in the NCEP Global Forecast System

AbstractThe impact of assimilating synoptic surveillance dropwindsonde data on the analysis and forecast of the structure and intensity of Tropical Storm Karen (2013) was examined. Data-denial experiments were conducted using the NCEP hybrid 3D ensemble–variational GSI and forecasts were made using the NCEP GFS model. The assimilation of dropwindsonde data resulted in a slightly more tilted tropical cyclone vortex, stronger vertical wind shear, and more upper-tropospheric dry air west of Karen in the initial conditions. These differences grew with time in the GFS forecasts, and resulted in a weaker and more sheared vortex by 24 h in the forecast that included the dropwindsonde data. After 24 h, the cyclone reintensified in the experiment where dropwindsonde data were excluded, likely because of moist processes in a favorable region for synoptic-scale ascent ahead of a baroclinic trough. In contrast, the forecast including the dropwindsonde data kept Karen weak and also did a better job forecasting the str.
Average-power scaling of self-heated Sr/sup +/ afterglow recombination lasers

The performance of a large-bore (25-mm) self-heated Sr/sup +/ (430.5-nm) recombination laser with longitudinal excitation is discussed in relation to the prospects for scaling average output power to the 5-10-W regime. Average-power scaling is found to be limited in large-bore laser tubes by slow interpulse thermal relaxation in the laser gas mixture with strong radial gradients in species' densities and temperatures at only modest pulse repetition frequencies, leading to premature termination of the population inversion on the tube axis. Proposals for circumventing these limitations in order to permit generation of multiwatt average laser output power at 430.5 nm from Sr/sup +/ are discussed. >
New class of solutions for water infiltration problems in unsaturated soils

This paper presents the results of approximate analytical solutions to Richards' equation, which governs the problem of unsaturated flow in porous media. The existing methods generally fall within the category of numerical and analytical methods, often having many restrictions for practical situations. In the present study, two approximate analytical methods known as the differential transform method (DTM) and homotopy perturbation method (HPM) were employed to find analytical solutions to Richards' equation. The methods were found to be robust in finding solutions practically identical to those from the existing analytical and numerical methods. Two representative examples were considered in order to evaluate the accuracy of the solutions obtained by DTM and HPM, revealing high level of accuracy in both cases.
Large eddy simulations of turbulent swirling flows in a dump combustor: a sensitivity study

Large eddy simulations (LES) of confined turbulent swirling flows in a model dump combustor are carried out. The simulations are based on a high‐order finite difference method on a Cartesian grid, with the sub‐grid scale stress tensor modelled using a scale‐similarity model. The aims of this work are to study the physics of the flow and to evaluate the performance of LES method for simulation of the major features of turbulent swirling flows—the vortex breakdown, the highly anisotropic and fast‐decaying turbulence structure. Influences of inflow/outflow conditions, combustor geometry, inlet swirl profile and Reynolds numbers on the vortex breakdown and turbulence structures are investigated. At very high swirl levels, the influence of the outflow conditions and the outlet geometry is fairly significant, not only at downstream near the outlet, but also at far upstream. At low Reynolds numbers, the onset of vortex breakdown is fairly sensitive to the change of Reynolds number; however, at high Reynolds numbers it is rather insensitive to the Reynolds number. Comparisons of LES results with experimental data are made. The LES results are shown to be in reasonably good agreement with the experimental data if appropriate inflow and outflow boundary conditions are imposed. Copyright © 2004 John Wiley & Sons, Ltd.
Excitation and propagation of surface electromagnetic waves studied by terahertz spectrochronography

We show the spectrochronography as an efficient tool to extend the THz time domain technique. Assuming that all the information is contained in the time-dependent electric field we apply a windowed transfer technique to measure the instantaneous spectra evolution. As an example, surface electromagnetic waves on the metal grating are considered. Dynamics of surface wave spectral component is measured.
Design of dynamic output feedback decentralized controllers via a separation procedure

This paper investigates the well-known separation properties that hold in the design of unconstrained output feedback controllers and tries to generalize them to cope with the design of structurally constrained decentralized controls. This problem, which until now has been open, presents additional constraints which destroy the useful properties that lead to separation. Necessary and sufficient conditions for decentralized stability and H2 norm minimization are given, providing a framework in which a suitable ad hoc separation procedure is developed. A numerical algorithm based on crossdecomposition is presented and applied in two situations: first, when separation fails to provide a feasible solution; and then, to improve the obtained controller. An example and a comprehensive benchmark illustrate and validate the method.
A super-resolution method for spatio-temporal plasma diagnostics

To study turbulence, high spatial and temporal resolution are required. In experiments, plasma diagnostics are characterized by low spatial and high temporal resolution. An adapted super-resolution algorithm is proposed to improve the spatial resolution by using temporal information. The performance of the super-resolution algorithm is compared with simple interpolation techniques. By means of synthetic data its performance is benchmarked.
Teaching conservation laws, symmetries and elementary particles with fast feedback

Lessons about elementary particles at the secondary school level can degenerate into listing a zoo of particles and reactions, resulting in disorganized and rather meaningless knowledge. A more powerful way is to focus on conservation laws, symmetries and reaction diagrams. The conservation laws and symmetries provide generalizing power that enables the students to predict whether or not certain reactions are possible and to derive new reactions from given ones by applying the symmetries. In this article we first present simplified Feynman diagrams and three symmetry operations. Then we discuss the fast feedback teaching method and present two lessons and a worksheet for teaching symmetries and reactions using this fast feedback. The method was developed and piloted during the last two school years in Dutch secondary schools.
On a problem of Hartman and Wintner

The Hartman–Wintner problem on asymptotic equivalence of fundamental systems of solutions (FSSs) for two Sturm–Liouville equations is studied. The following results are obtained: a criterion of asymptotic equivalence of FSSs, and sufficient conditions of asymptotic equivalence of FSSs which are expressed in terms of the coefficients of the considered equations only.
On the Performance of the H-H Test

Horowitz and HardIe (1992) proposed a procedure for testing a parametric model against a semiparametric alternative (called the H-H test) which is based on the evaluation of moment conditions following the methodology presented by Newey (1985). Their approach is related to Bierens (1990) test to detect any kind of model misspecification also based on Newey's framework. It is shown that these tests procedures are consistent (the asymptotic power is equal to 1 in the set of alternatives). However the absence of information about their finite sample properties make simulations required to evaluate their quality on discriminating model misspecification. In this paper the small sample performance of the H-H test is analized concerning the empirical power and size by a Monte Carlo study with single index models. The results are compared with those obtained using Bierens' test.
Holographic testing of terahertz antennas

In the light of future applications involving terahertz antenna measurements, this paper revisits Gabor (1949) holography as a direct method for recovering phase, offering some interesting advantages for near-field measurements. In particular, we examine the theory and parameterization of planar near-field Gabor holography and comment on the requirements for scanner precision at terahertz frequencies.
Bayesian Binomial Regression: Predicting Survival at a Trauma Center

Abstract Standard methods for analyzing binomial regression data rely on asymptotic inferences. Bayesian methods can be performed using simple computations, and they apply for any sample size. We provide a relatively complete discussion of Bayesian inferences for binomial regression with emphasis on inferences for the probability of “success. ” Furthermore, we illustrate diagnostic tools, perform model selection among nonnested models, and examine the sensitivity of the Bayesian methods.
Inverse problems: A Bayesian perspective

The subject of inverse problems in differential equations is of enormous practical importance, and has also generated substantial mathematical and computational innovation. Typically some form of regularization is required to ameliorate ill-posed behaviour. In this article we review the Bayesian approach to regularization, developing a function space viewpoint on the subject. This approach allows for a full characterization of all possible solutions, and their relative probabilities, whilst simultaneously forcing significant modelling issues to be addressed in a clear and precise fashion. Although expensive to implement, this approach is starting to lie within the range of the available computational resources in many application areas. It also allows for the quantification of uncertainty and risk, something which is increasingly demanded by these applications. Furthermore, the approach is conceptually important for the understanding of simpler, computationally expedient approaches to inverse problems.
Quasi-Birth-and-Death Processes with an Explicit Rate Matrix

We determine the equilibrium distribution for a class of quasi-birth-and-death (QBD) processes using the matrix-geometric method, which requires the determination of the rate matrix R. In contrast to most QBD processes, the class under consideration allows for an explicit description of R, by exploiting its probabilistic interpretation. We show that the problem of finding each element of R reduces to counting lattice paths in the transition diagram. For resolving this counting problem, we present an extended version of the classical Ballot theorem. We also present various examples of queueing models that fit into the class.
Umbrella spherical integration: a stable meshless method for non‐linear solids

A stable meshless method for studying the finite deformation of non‐linear three‐dimensional (3D) solids is presented. The method is based on a variational framework with the necessary integrals evaluated through nodal integration. The method is truly meshless, requiring no 3D meshing or tessellation of any form. A local least‐squares approximation about each node is used to obtain necessary deformation gradients. The use of a local field approximation makes automatic grid refinement and the application of boundary conditions straightforward. Stabilization is achieved through the use of special ‘umbrella’ shape functions that have discontinuous derivatives at the nodes. Novel efficient algorithms for constructing the nodal stars and computing the nodal volumes are presented. The method is applied to four test problems: uniaxial tension, simple shear and bending of a bar, and cylindrical indentation. Convergence studies at infinitesimal strain show that the method is well‐behaved and converges with the number of nodes for both uniform and non‐uniform grids. Typical of meshless methods employing nodal integration, the total energy can be underestimated due to the approximate integration. At finite deformation the method reproduces known exact solutions. The bending example demonstrates an interesting example of torsional buckling resulting from the bending. Copyright © 2006 John Wiley & Sons, Ltd.
Inference on rare errors using asymptotic expansions and bootstrap calibration

The number of items in error in an audit population is usually quite small, whereas the error distribution is typically highly skewed to the right. For applications in statistical auditing, where line item sampling is appropriate, a new upper confidence limit for the total error amount in an audit population is obtained. Our method involves an empirical Cornish-Fisher expansion in the first place; in the second stage we employ the bootstrap to calibrate the coverage probability of the resulting interval estimate.