Miracle-dz/UniFAR-FTUs huggingface dataset:
A dispersion-relation preserving fourth-order compact time-domain/frequency-domain finite-volume method for computational acoustics

A method for directly computing acoustic signatures without a wave equation analogy is presented. The governing acoustic equations are derived from the unsteady Euler equations by linearizing about a steady mean flow and by assuming a single frequency disturbance. A pseudo-time variable is introduced, and the entire set of equations is driven to convergence by a point-implicit four-stage Runge-Kutta time-marching finite-volume scheme. The spatial terms are discretized using a compact fourth-order-accurate dispersion-relation-preserving scheme. A compact sixth-order-accurate dissipation operator is intr oduced to damp out physically nonrealizable spurious modes which are the artifact of numerical discretizaton. A new formulation of the farfield causality condition is presented which is based on the modal analysis of the similarity form of the linearized Euler equations. The method was applied to compute acoustic radiation from compact and noncompact oscillating airfoils in the presence of mean flow, acoustic radiation due to airfoil/gust interactions, acoustic scattering from airfoils, and wave propagation in ducts. Results are compared with known analytical solutions and the results of other investigators, where applicable. (Author)
Reflectivity and Optical Brightness of Laser-Induced Shocks in Silicon

We report the first simultaneous measurement of the reflectivity and optical emission of a strong (4\char21{}8 Mbar) shock front emerging at a free surface of a solid. Planar shock waves were driven by thermal x rays from a laser-heated cavity. The inferred model-independent brightness temperature of the shock front in silicon turns out to be significantly below the expected Hugoniot temperature. We find that our data cannot be explained within the two-temperature model which assumes instantaneous metallization of silicon in the density jump.
Equivalent circuit synthesis for a loop antenna based on the singularity expansion method

The singularity expansion method (SEM) is used to derive active equivalent circuits for a plane-wave-excited loop antenna immersed in a lossless and homogeneous medium. The circuits consist of simple modules associated with the dominant pole pairs of the loop, and circuit element values are expressed in terms of the SEM data. Particular attention is paid to the issue of physical realizability. The synthesized circuits have been analyzed under various excitation and loading conditions by a general-purpose circuit analysis code, and the results agree favorably with the responses of the loop computed by other means
Vortex Patterns in Ginzburg-Landau Minimizers

We present a survey of results obtained with Etienne Sandier on vortices in the minimizers of the 2D Ginzburg-Landau energy of superconductivity with an applied magnetic field, in the asymptotic regime of large kappa where vortices become pointlike. We decribe results which characterize the critical values of the applied field for which vortices appear, their numbers and locations. If the applied field is large enough, it is observed in experiments that vortices are densely packed and form triangular (hexagonal) lattices named Abrikosov lattices. Part of our results is the rigorous derivation of a mean field model describing the optimal density of vortices at leading order in the energy, and then the derivation of a next order limiting energy which governs the positions of the vortices after blow-up at their inter-distance scale. This limiting energy is a logarithmic-type interaction between points in the plane. Among lattice configurations it is uniquely minimized by the hexagonal lattice, thus providing a first justification of the Abrikosov lattice in this regime.
Spectral Analysis of Non-Uniformly Sampled Data: A New Approach Versus the Periodogram

We begin by revisiting the plain least-squares periodogram (LSP) for real-valued data. Then we introduce a new method for spectral analysis of non-uniformly sampled data by "iteratively weighting LSP", and we name the new method real-valued iterative adaptive approach (RIAA). LSP and RIAA are most suitable for data sequences with discrete spectra. For such type of data, we present a procedure to obtain a parametric spectral estimate, from the LSP or RIAA non-parametric estimate, by means of the Bayesian information criterion (BIC). We also discuss a possible strategy for designing the sampling pattern of future measurements. Several numerical examples are provided to illustrate the performance of our proposed approaches.
Time-Series Forecast Jointly Allowing the Unit-Root Detection and the Box–Cox Transformation

ABSTRACT An information-criterion-based model-selection method is presented for forecasting that allows for the unit-root detection and the Box–Cox transformation simultaneously. In this method, a battery of alternative models with and without unit root is considered changing the order of autoregressive process and the Box–Cox parameter, and the best model is selected using information criteria. Simulation results suggest that the Bayesian information criterion (BIC) outperforms the bias-corrected Akaike information criterion (AICc) and that the augmented Dickey–Fuller test performs worse in the case of incorrect data transformation. The results of forecasting quarterly time series of industrial production indicate that the BIC-based method outperforms the other conventional methods.
Sound propagation in an urban environment

This thesis concerns the modelling of sound propagation in an urban environment. For most of the thesis a point source of sound source is assumed, and both 2D and 3D geometries are considered. Buildings are modelled as rigid blocks, with the effects of surface inhomogeneities neglected. In the time-harmonic case, assuming that the wavelength is short compared to typical lengthscales of the domain (street widths and lengths), ray theory is used to derive estimates for the time-averaged acoustic power flows through a network of interconnecting streets in the form of integrals over ray angles. In the impulsive case, the propagation of wave-field singularities in the presence of obstacles is considered, and a general principle concerning the weakening of singularities when they are diffracted by edges and vertices is proposed. The problem of switching on a time-harmonic source is also studied, and an exact solution for the diffraction of a switched on plane wave by a rigid half-line is obtained and analysed. The pulse diffraction theory is then applied in a study of the inverse problem for an impulsive source, where the aim is to locate an unknown source using Time Differences Of Arrival (TDOA) at multiple receivers. By using reflected and diffracted pulse arrivals, the standard free-space TDOA method is extended to urban environments. In particular, approximate source localisation is found to be possible even when the exact building distribution is unknown.
Aerosol Characterization by Dual-Wavelength Polarization Lidar Measurements over Kochi, Japan during the Warm Seasons of 2008 to 2010

Dual-wavelength polarization lidar measurements of aerosols and clouds were conducted over Kochi (33.6°N, 133.5°E) during the warm-season field campaign of the Japanese Cloud Seeding Experiment Precipitation Augmentation project in June̶July of 2008 to 2010. Lidar-derived aerosol optical properties were compared with the microphysical properties obtained with aircraft-based instruments to evaluate the utility of the lidar data for characterizing the background aerosol, which critically affects the success of cloud seeding to enhance precipitation. The results showed that the particle backscattering coefficient at 532 nm correlated well with the number concentration of aerosols with diameter (Dp) exceeding 0.3 μm (correlation coefficient, r = 0.89), whereas the correlation of the backscattering coefficient with the number concentration of cloud condensation nuclei (CCN), activated at a water saturation of 0.7% or 1.0%, was lower (r = 0.74) because of the low sensitivity of the lidar system to the small CCN particles (Dp ≈ 0.04 μm). In lidar data collected on 1 July 2008, the depolarization ratio (δ) was high (20%), and the backscatter wavelength exponent (å) was low ( < 0.5) between altitudes of 4 and 6 km, and they were low (δ = 2.5%) and moderate (å = 0.7) between 0.5 and 1.0 km, suggesting the presence of supermicrometer-sized, non-spherical particles in the upper altitude range and a predominance of submicrometer-sized particles and/or spherical particles in the lower altitude range. These values were consistent with aircraft measurements, indicating the presence of supermicrometer-sized mineral particles in the upper altitude range and a predominance of submicrometer-sized sulfates and supermicrometer-sized sea-salt droplets at lower altitude. Our results demonstrate the utility of lidar data for aerosol characterization, although the further improvement of CCN characterization by lidar is necessary.
Asymptotic expansions of the null distributions of three test statistics in a nonnormal GMANOVA model

This paper deals with three test statistics for testing a linear hypothesis and estimators of regression coe1⁄2cients in the GMANOVA model which was proposed by Potthof and Roy (1964), without assuming normal error. The test statistics considered include the likelihood ratio statistic, the Lawley-Hotelling trace criterion and the Bartlett-Nanda-Pillai trace criterion, which have been proposed under normality. We obtain asymptotic expansions of the null distributions of three test statistics up to the order nÿ1, where n is the sample size. The results are generalizations of the formulas in Wakaki, Yanagihara and Fujikoshi (2000). In addition, asymptotic expansions of the distribution functions of several standardized statistics on regression coe1⁄2cients are derived.
Bend-insensitive single-mode photonic crystal fiber with ultralarge effective area for dual applications

Abstract. A novel photonic crystal fiber (PCF) having circular arrangement of cladding air holes has been designed and numerically optimized to obtain a bend insensitive single mode fiber with large mode area for both wavelength division multiplexing (WDM) communication and fiber-to-the-home (FTTH) application. The bending loss of the proposed bent PCF lies in the range of 10−3 to 10−4 dB/turn or lower over 1300 to 1700 nm, and 2 × 10−4 dB/turn at the wavelength of 1550 nm for a 30-mm bend radius with a higher order mode (HOM) cut-off frequency below 1200 nm for WDM application. When the whole structure of the PCF is scaled down, a bending loss of 6.78×10−4 dB/turn at 1550 nm for a 4-mm bend radius is obtained, and the loss remains in the order of 10−4 dB/turn over the same range of wavelength with an HOM cut-off frequency below 700 nm, and makes the fiber useful for FTTH applications. Furthermore, this structure is also optimized to show a splice loss near zero for fusion-splicing to a conventional single-mode fiber (SMF).
Topological aspects of three-dimensional wakes behind rotary oscillating cylinders

The development of a three-dimensional viscous incompressible flow generated behind an infinitely long circular cylinder, impulsively started into rectilinear motion and rotationally oscillating, is studied computationally. The numerical scheme, an hybrid vortex method, is used to integrate the velocity–vorticity formulation of the Navier–Stokes equations. The Reynolds number considered is $\Rey\,{=}\,400$, which is moderate though beyond the critical values $\Rey_2\,{\simeq}\,190$ and $\Rey_2'\,{\simeq}\,260$ for which the flow becomes spontaneously three-dimensional. The numerical method is explained and its main points are developed. This scheme is then applied to solve some two-dimensional problems, both in order to validate the method and to compute a nominal two-dimensional flow, required to measure the impact of three-dimensionality. The three-dimensional flow past a steady cylinder is also compared to benchmark simulations. Once the flow has become fully three-dimensional, beyond the transient regime and saturation of instabilities, the cylinder begins a rotary oscillation around its axis. Two kinds of rotations are considered: constant amplitude and several frequencies, and constant frequency and various amplitudes. When amplitude and frequency are high enough, the whole flow comes back to its two-dimensional state. This result gives a justification for two-dimensional computations in the literature related to rotating cylinders. For the first super-harmonic frequency of the flow, a parametric study is performed in order to find the impact of the amplitude on the topology of the flow. A bifurcation is clearly identified. Finally, the mechanisms involved in the return to a two-dimensional state are explained: the interaction between transverse instabilities and von Kármán streets is quantified by means of a correlation analysis.
Huge electric field enhancement and highly sensitive sensing based on the Fano resonance effect in an asymmetric nanorod pair

A sharp plasmonic Fano resonance is found to appear in a silver nanorod pair structure with broken length symmetry. It is shown that it arises from strong interference between a narrow plasmon mode of inter-nanorod near-field coupling and broad scattering from the nanorod. The inter-nanorod coupling is the result of the magnetic dipole plasmon resonance induced by the anti-parallel current of the nanorod pair, while the broad scattering is caused by electric dipole oscillation. The numerical results show that a giant local field enhancement (197), a high quality factor (52) and a sensing sensitivity of 1426 nm per refractive index unit in the symmetry-broken nanorod pair with a displacement Δl = 40 nm originated from a pronounced Fano resonance in the near-infrared spectrum. Huge local field enhancement and high sensitivity make this simple structure promising for surface enhanced Raman spectroscopy and sensing applications.
Simple equations for the magnetization and reluctivity curves of steel

The normal B-H curves of several types of steel are shown to be approximated by the equation H= (k_{1} e^{k_{2}B^{2}} + k_{3}) B . The reluctivity ( H/B ) and its derivative with respect to B are given by simple equations that are especially useful in the finite element method of analyzing steel magnetic circuits.
Molecular Hydrogen in the IRAS 03282+3035 Stellar Jet

We detected shock-excited 2.122 μm molecular hydrogen from the blueshifted lobe of the highly collimated CO outflow associated with the young stellar object IRAS 03282+3035 in the Perseus molecular cloud. The H 2 emission has a peak surface brightness of 5×10 -4 ergs s -1 cm -2 sr -1 , making this one of the brightest shock-excited molecular hydrogen sources associated with a low-mass young stellar object. The emission has knotty structure with faint tails lying parallel to the mean outflow axis. These knots coincide with molecular bullets B3 and B4 located near the end of the highest velocity CO-emitting component and may be bow shocks where a fast jet interacts with the surrounding medium. The bulk of the lower velocity CO emission is located downwind from the H 2 emission zone
COMPLEXITY RESULTS FOR BANDWIDTH MINIMIZATION

We present a linear-time algorithm for sparse symmetric matrices which converts a matrix into pentadiagonal form (“bandwidth 2”), whenever it is possible to do so using simultaneous row and column permutations. On the other hand when an arbitrary integer k and graph G are given, we show that it is $NP$-complete to determine whether or not there exists an ordering of the vertices such that the adjacency matrix has bandwidth $ \leqq k$, even when G is restircted to the class of free trees with all vertices of degree $ \leqq 3$. Related problems for acyclic directed graphs (upper triangular matrices) are also discussed.
THE LEFSCHETZ CONDITION ON PROJECTIVIZATIONS OF COMPLEX VECTOR BUNDLES

We consider a condition under which the projectivization P (Ek) of a complex k-bundle Ek → M over an even-dimensional manifold M can have the hard Lefschetz property, affected by [4]. It depends strongly on the rank k of the bundle Ek. Our approach is purely algebraic by using rational Sullivan minimal models [2]. We will give some examples. The contents of this paper is according to [6]. A Poincare duality space Y of the formal dimension fd(Y ) = max{i;H (Y ;Q) = 0} = 2m is said to be cohomologically symplectic (c-symplectic) if u = 0 for some u ∈ H(Y ;Q) and, furthermore, is said to have the hard Lefschetz property (or simply the Lefschetz property) with respect to the c-symplectic class u, if the maps ∪u : Hm−j(Y ;Q) → H(Y ;Q) 0 ≤ j ≤ m are monomorphisms (then called the Lefschetz maps) [7]. (Then we often say that H∗(Y ;Q) is a Lefschetz algebra [4]. ) For example, a compact Kahler manifold has the hard Lefschetz property [7], [3, Theorem 4.35]. Let M be an even-dimensional manifold and ξ : E → M be a complex k-bundle over M . The projectivization of the bundle ξ P (ξ) : CP k−1 j → P (E) → M satisfies the rational cohomology algebra condition (∗) : H∗(P (E);Q) = H∗(M ;Q)[x] (xk + c1xk−1 + · · ·+ cjxk−j + · · ·+ ck−1x+ ck) where ci are the Chern classes of ξ and x is a degree 2 class generating the cohomology of the complex projective space fiber (Leray-Hirsch theorem) [1], [4], [7, p.122]. The manifold P (E) appears as the exceptional divisor in blow-up construction for a certain embedding of M [5], [7, Chap.4]. When M is a non-toral symplectic nilmanifold of dimension 2n, there is a bundle E such that P (E) is not Lefschetz [8], [4, Example 4.4]. In general, for a 2k-dimensional manifold M and a fibration
Calibration of stochastic volatility models

Calibration of stochastic volatility models by Yavor Kovachev This thesis examines the performance of three methods for calibrating advanced option pricing models incorporating stochastic volatility. We examine the Heston, Bates, Barndorff-NielsenShephard (BNS) and the stochastic time change Normal Inverse Gaussian Cox Ingersoll Ross (NIG-CIR) models. The calibration methods used are hybrid particle swarm optimization (PSO) combined with a gradient based interior point algorithm, a genetic algorithm (GA) combined with a gradient based interior point algorithm and an interior point algorithm alone. We show that while standard methods can in general be successfully applied, they also fail catastrophically and are not suitable for the calibration of the NIG-CIR model. Additionally, we demonstrate that perfect calibration in term of minimizing the difference between market and model prices as well as between synthetic and model parameters can be achieved only in the case of the Heston and NIG-CIR models. These findings suggest that unlike the Bates and BNS models, the Heston and NIG-CIR models are well specified and lead to stable Greek values making them suitable for the pricing, hedging and risk management of exotic derivatives.
Modeling alkalosis ordinal data using different link functions

Abstract Major decisions in the model building for ordinal regression involve the choice of the appropriate link function, as well as the decision for the explanatory variables to be included. This study aims to apply ordinal regression models to medical data used to describe the metabolic disorder alkalosis which is expressed in an Intensive Care Unit. Saturated and nested models are fitted with the use of five different link functions and stepwise methods are also applied. Differences involving variable selection and goodness of fit measures were observed and models were evaluated. A review of two well-known statistical software procedures for data analysis is also presented and useful conclusions are drawn.
Filamentation of Alfvén waves associated with transverse perturbation

This paper presents an investigation of the growth of a Gaussian perturbation on a uniform plane wave front of an Alfven wave (AW). The effect of the nonlinear coupling between the main AW and the perturbation has been studied. The dynamical equation for the field of the perturbation has been established and its semianalytical solution has been obtained in low (β≪me/mi) and high (β≫me/mi) β cases (β≪1). The critical field of the perturbation has been evaluated for the given size of the perturbation for its filamentation process (hot spot formation). Nonlinear evolution of the perturbation into filamentary structures and its dependence on various parameters of the solar wind and corona has been investigated in detail.
Experimental Characterization of a Nickel Alloy-Based Manifold-Microgroove Evaporator

Effective heat and mass exchangers are vital for further improvement of absorption cooling systems. In the current study, a novel manifold-microchannel evaporator was developed and tested. This paper reports heat transfer coefficients and pressure drop for a nickel alloy-based tubular microgrooved evaporator consisting of a novel manifold guided flow. The evaporator was designed for refrigerant-to-liquid heat exchange, and the heat transfer surface consisted of fine high-aspect-ratio microchannels having 100 μm channel width and 600 μm channel height. The refrigerant-side flow was guided through square manifold feeds with sides of 2 mm in length. A tube insert providing an annular gap of 2.5 mm was used on the water side. Experiments were conducted with R134a as the refrigerant for a flow rate range of 5–30 g/s and water-side flow rate range of 100–600 ml/s. An overall heat transfer coefficient of more than 10,000 W/m2-K was measured with a modest maximum pressure drop of 120 mbars and 100 mbars on the refrigerant and water sides, respectively.
Time-domain synthesis via Walsh functions

The paper deals with the application of Walsh functions to the time-domain-synthesis problem, i.e., the determination of a suitable internal structure for a system from its prescribed external (input/output) behaviour. The method is based on repeated integration, and a new operational matrix, which relates Walsh functions and their integrations, is defined. Examples of transfer-function and state-equation synthesis are used to illustrate the technique.
Response Error in a Transformation Model with an Application to Earnings-Equation Estimation

This paper considers estimation of a transformation model in which the transformed dependent variable is subject to classical measurement error. We consider cases in which the transformation function is known and unspecified. In special cases (e.g. log and square-root transformations), least-squares or non-linear least-squares estimators are applicable. A flexible approximation approach (based on Taylor expansion) is proposed for a parametrized transformation function (like the Box--Cox model), and a semi-parametric approach (combining a semi-parametric linear-index estimator and non-parametric regression) is proposed for the case of an unspecified transformation function. The methods are applied to the estimation of earnings equations, using wage data from the Current Population Survey (CPS). Copyright Royal Economic Socciety 2004
Measurement of the average size and density of clusters in a gas jet

We present an all-optical method for measurement of the average size and density of clusters produced by high-pressure gas jet flow. The technique employs Rayleigh scattering imaging combined with interferometry. The cluster size and density in a gas jet under the irradiation of intense laser fields plays a critical role in the laser–cluster coupling dynamics.