Miracle-dz/UniFAR-FTUs huggingface dataset:
Properties of the third harmonic of the radiation from self-amplified spontaneous emission free electron laser

Recent theoretical and experimental studies have shown that the self-amplified spontaneous emission free-electron laser (SASE FEL) with a planar undulator holds a potential for generation of relatively strong coherent radiation at the third harmonic of the fundamental frequency. Here we present a detailed study of the nonlinear harmonic generation in the SASE FEL obtained with a time-dependent FEL simulation code. Using similarity techniques we present universal dependencies for temporal, spectral, and statistical properties of the odd harmonics of the radiation from SASE FEL. In particular, we derived universal formulas for radiation power of the odd harmonics at saturation. It was also found that coherence time at saturation falls inversely proportional to the harmonic number, and relative spectrum bandwidth remains constant with the harmonic number.
Lattice BGK Models for Navier-Stokes Equation

We propose the lattice BGK models, as an alternative to lattice gases or the lattice Boltzmann equation, to obtain an efficient numerical scheme for the simulation of fluid dynamics. With a properly chosen equilibrium distribution, the Navier-Stokes equation is obtained from the kinetic BGK equation at the second-order of approximation. Compared to lattice gases, the present model is noise-free, has Galileian invariance and a velocity-independent pressure. It involves a relaxation parameter that influences the stability of the new scheme. Numerical simulations are shown to confirm the speed of sound and the shear viscosity.
Transport properties of a many-valley semiconductor

The simple model of a semiconductor, based on a single effective mass for the charge carriers and a spherical shape for the surfaces of constant energy, is now known to be inadequate for most of the semiconductors which have been extensively studied experimentally. However, some of these do correspond to what may be called the “many-valley” model, a model for which the band edge occurs at a number of equivalent points K(i) in wave number space, and for which the surfaces of constant energy are multiple ellipsoids, one centered on each of these points. This paper develops, for models of this type, the theory for: mobility (Section 2) and its temperature dependence (Section 3); thermoelectric power (Section 4); piezoresistance (Section 5); Hall effect (Sections 6 and 9); high-frequency dielectric constant (Section 7); and magnetoresistance (Sections 8 and 9). These phenomena are treated, for cases to which Maxwellian statistics apply, on the assumption that the scattering of the charge carriers is describable by a relaxation time which depends on energy only, but is otherwise unrestricted. This assumption can be shown to be justified in a large class of cases, although for some cases it fails, notably when ionized impurity scattering predominates and at the same time the effective mass is very anisotropic. Special attention is given to the role of inter-valley lattice scattering, i.e., to processes whereby a charge carrier is scattered from the neighborhood of one of the band edge points
Statistical estimation of the structure of a finite population

A survey of recent advances in the problem of estimating the structure of a finite population is given. We include into the survey the results closely connected with the allocation problem and consider both homogeneous and stratified populations. A comparative analysis of the results obtained by using sufficiency and likelihood principles is carried out for a general sampling scheme. The asymptotical approach is also presented. The optimal (asymptotically optimal) inferences for both point and confidential estimation are the main object of the article. Possible extensions of the investigations in this area are also discussed.
Eigenmode analysis of photoacoustic sensors via finite element method

In the field of photoacoustic sensors, research has mainly been concentrating on the investigation of cylinder shaped cells. For cylinder cells, important acoustical properties can be obtained by analytical methods. In recent years, cells with other shapes have come into focus. In these cases, the sound spectrum and other quantities of interest cannot be obtained by analytical means. Finite element tools, however, are well suited to deal with unconventional geometries. In this article we present results concerning the eigenmodes of T-shaped photoacoustic cells.
Unified split-step precise integration timedomain method for dispersive media

Based on the use of auxiliary differential equations, a unified split-step precise integration time-domain (SS-PITD) method is proposed for modelling wave propagation in linear dispersive media. The unification of this method is achieved by using a general expression to represent the Debye, Lorentz and Drude dielectric medium models. Moreover, due to the introduction of the SS scheme, the original two-dimensional (2D) or 3D electromagnetic problem reduces to a set of 1D sub-problems which can be efficiently solved by using the conventional PITD algorithm. It leads to a great reduction in the requirement of computation time and storage space. The proposed method is verified with a numerical example and compared with the finite-difference time-domain method.
Residual energy of linear prediction applied to vowel and speaker recognition

Recognition of steady-state vowels based on the residual energy of linear prediction was ascertained to be useful for a recognition system in which the reference data are taken from the intended speaker. Sharp speaker selectivity based on a threshold criterion suggests that the use of the residual signal energy may also be useful for speaker identification, especially for speaker screening in a large population.
Electromagnetic Field Expansions in Loss‐Free Cavities Excited through Holes

It is shown that the electromagnetic field in a loss‐free cavity excited through holes cannot be completely expressed in terms of the short‐circuit modes of the cavity satisfying the condition that the tangential component of the electric field is zero on the boundary of the cavity including the openings. For a complete expansion it is necessary to add an irrotational magnetic field, which contributes a term inversely proportional to the frequency, to the usual admittance matrix. If the cavity is presumed to include a reasonable portion of the guides feeding the openings, this irrotational component becomes almost diagonal.
Variability estimation of hue and saturation components in the HSV space

When dealing with hue-saturation-value (HSV) components, one must be very careful about nonlinearity and singularities of the HSV space, which can amplify considerably the sampling errors of the original components, namely, red-green-blue (RGB) channels. Contradictorily, almost all research in computerized image analysis or processing based on HSV (or other nonlinear color space) neglect to account for such inhomogeneous variability. In this article, we present two approaches for estimating the degree of variability of hue and saturation in the HSV space, intended to assist any color image processing or analysis based on such components. Both approaches end up with new estimators of the hue and saturation standard deviation for a pixel distribution of any color sample. The first approach consists in applying error-propagation analysis on the RGB-to-HSV formulation and the second one is based on heuristic rules inferred from geometrical relations between HSV values of pixel distributions. Experiments show that introduced estimators provide very accurate predictions of true H-S deviations obtained from a broad subset of 183 NCS® color samples. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011
Automated integration of lidar into the LANDFIRE product suite

Accurate information about three-dimensional canopy structure and wildland fuel across the landscape is necessary for fire behaviour modelling system predictions. Remotely sensed data are invaluable for assessing these canopy characteristics over large areas; lidar data, in particular, are uniquely suited for quantifying three-dimensional canopy structure. Although lidar data are increasingly available, they have rarely been applied to wildland fuels mapping efforts, mostly due to two issues. First, the Landscape Fire and Resource Planning Tools (LANDFIRE) program, which has become the default source of large-scale fire behaviour modelling inputs for the US, does not currently incorporate lidar data into the vegetation and fuel mapping process because spatially continuous lidar data are not available at the national scale. Second, while lidar data are available for many land management units across the US, these data are underutilized for fire behaviour applications. This is partly due to a lack of local personnel trained to process and analyse lidar data. This investigation addresses these issues by developing the Creating Hybrid Structure from LANDFIRE/lidar Combinations (CHISLIC) tool. CHISLIC allows individuals to automatically generate a suite of vegetation structure and wildland fuel parameters from lidar data and infuse them into existing LANDFIRE data sets. CHISLIC will become available for wider distribution to the public through a partnership with the U.S. Forest Service’s Wildland Fire Assessment System (WFAS) and may be incorporated into the Wildland Fire Decision Support System (WFDSS) with additional design and testing. WFAS and WFDSS are the primary systems used to support tactical and strategic wildland fire management decisions.
Towards Parking Lot Occupancy Assessment Using Aerial Imagery and Computer Vision

Advances in Computer Vision and Aerial Imaging have enabled countless downstream applications. To this end, aerial imagery could be leveraged to analyze the usage of parking lots. This would enable retail centres to allocate space better and eliminate the parking oversupply problem. With this use case in mind, the proposed research introduces a novel framework for parking lot occupancy assessments. The framework consists of a pipeline of components that map a sequence of image sets spanning a parking lot at different time intervals to a parking lot turnover heatmap that encodes the frequency each parking stall was used. The pipeline of components includes Image Stitching, Vehicle Detection and Heatmap Generation. The focus of this work is Image Stitching and Vehicle Detection, while Heatmap Generation is left for future work. Beyond proposing a novel framework for parking lot occupancy assessments, several contributions are made to the Computer Vision field. In particular, a novel method for initializing the pose of images based on the metadata from the acquisition system is introduced. Additionally, a novel comparative study of object detection models applied to the vehicle detection task is presented. Extensive experiments are used to validate the proposed contributions on both public and private datasets.
A Vertical Insulated Gate AlGaN/GaN Heterojunction Field-Effect Transistor

We fabricated a vertical insulated gate AlGaN/GaN heterojunction field-effect transistor (HFET), using a free-standing GaN substrate. This HFET has apertures through which the electron current vertically flows. These apertures were formed by dry etching the p-GaN layer below the gate electrodes and regrowing n--GaN layer without mask. The HFET exhibited a specific on-resistance of as low as 2.6 mΩ·cm2 with a threshold voltage of -16 V. This HFET would be a prototype of a GaN-based high-power switching device.
Trimmed $k$-means: an attempt to robustify quantizers

A class of procedures based on impartial trimming (self-determined by the data) is introduced with the aim of robustifying k-means, hence the associated clustering analysis. We include a detailed study of optimal regions, showing that only nonpathological regions can arise from impartial trimming procedures. The asymptotic results provided in the paper focus on strong consistency of the suggested methods under widely general conditions. A section is devoted to exploring the performance of the procedure to detect anomalous data in simulated data sets.
Molecule Formation and Infrared Emission in Fast Interstellar Shocks. III. Results for J Shocks in Molecular Clouds

The structure and emission spectrum of J shocks in molecular gas are studied over a broad range of conditions. It is found that at high densities chemistry has a profound effect on the emission spectrum: the density behind the shock is sufficiently high that some of the internal energy of the newly formed H2 molecules is transformed to the gas as heat by collisional deexcitations, producing the H2 formation plateau. In this temperature plateau, endothermal reactions and neutral-neutral chemical reactions with activation energies can proceed efficiently, producing significant quantities of warm H2, CO, OH, and H2O and enhanced columns of warm atoms and ions. The heat generated by the H2 formation is radiated in collisionally excited atomic fine-structure lines. 129 refs.
Multiple scattering in the presence of absorption: a theoretical treatment for quasi one-dimensional systems

We consider propagation of waves in a disordered medium, extending the treatment of quasi one-dimensional systems, due to Dorokhov and to Mello et al to include absorption. In particular, we obtain within this approach the probability distribution of the reflection matrix for a semi-infinite system, as a function of the ratio of the mean free paths for absorption and scattering.
Far field characterization of diffracting circular apertures

The far field angular intensity distribution I(θ) of the λ=633 nm radiation transmitted through diffracting circular apertures is measured for diameters ranging between 60 and 500 nm. The circular apertures are located at the apex of aluminum coated tapered optical fiber tips. I(θ) depends sensitively on the aperture diameters down to λ/6. This property is used to determine the optical aperture size of metal coated tapered optical fiber tips used for near field scanning optical microscopy.
Free-carrier electro-absorption and electro-refraction modulation in group IV materials at mid-infrared wavelengths

Mid-infrared group IV photonics is emerging as a field with possible applications ranging from gas sensing to free-space communications. Free-carrier induced electro-absorption and electro-refraction have become the most widely used modulation mechanisms in active near-infrared silicon photonic devices. This work examines the magnitude of this effect in group IV materials at mid-infrared wavelengths. In silicon electro-absorption effects are calculated from experimental absorption coefficient data, and electro-refraction is calculated through numerical Kramers-Kronig analysis of absorption spectra. In germanium the Drude-Lorentz equations are used to estimate both change in absorption and change in refractive index.
The heat budget of a midlatitude squall line and implications for potential vorticity production

Abstract The water and heat budgets for a midlatitude squall line are estimated from single- and dual-Doppler-radar data and thermodynamic data from rawinsonde and thermodynamic retrieval (from dual-Doppler winds). These data, along with models to retrieve the freezing, melting, and radiative heating rates, yield vertical profiles of the heating within the convective, stratiform, and overhanging anvil areas of the squall line and differentiate the processes contributing to the total heating. The use of radar-derived vertical velocity information provides a more accurate delineation of the convective and stratiform components of the heating than can be obtained from rawinsonde data. The effects of diabatic heating on the potential vorticity (PV) field are calculated using a simple two-dimensional model and the vertical profiles of heating from the heat budget. The diabatic heating produced a deep column of high PV air coincident with the convective region and produced several regions of negative PV. Simila.
Operational Assimilation of GPS Zenith Total Delay Observations into the Met Office Numerical Weather Prediction Models

AbstractZenith total delay (ZTD) observations derived from ground-based GPS receivers have been assimilated operationally into the Met Office North Atlantic and European (NAE) numerical weather prediction (NWP) model since 2007. Assimilation trials were performed using the Met Office NAE NWP model at both 12- and 24-km resolution to assess the impact of ZTDs on forecasts. ZTDs were found generally to increase relative humidity in the analysis, increasing the humidity bias compared to radiosonde observations, which persisted through the forecasts at some vertical levels. Improvements to cloud forecasts were also identified. Assimilation of ZTDs using both three-dimensional and four-dimensional variational data assimilation (3D-Var/4D-Var) was investigated, and it is found that assimilation at 4D-Var does not deliver any clear benefit over 3D-Var in the periods studied with the NAE model. This paper summarizes the methods used to assimilate ZTDs at the Met Office and presents the results of impact trials pe.
Testing the local applicability of MODIS BRDF parameters for correcting Landsat TM imagery

Landsat Thematic Mapper (TM) imagery is widely used for large scale multi-temporal monitoring of the land surface. One source of variability in this imagery, which is not related to variation in the land surface, is the result of the bi-directional reflectance distribution function (BRDF). This causes variation in the measured reflectance as a function of the angular configuration of the sun and sensor. To remove this variation from the imagery, a correction can be applied for BRDF. Some authors have proposed the use of the BRDF parameterization derived for the Moderate Resolution Imaging Spectroradiometer (MODIS; NASA, Washington, DC, USA) instrument as a means of correction for BRDF in Landsat TM imagery. However, since the spatial scale of the two instruments is substantially different, it is not clear up to what extent the MODIS BRDF parameters are applicable to Landsat TM. This study provides a direct empirical test of this, over the eastern Australian landscape, and tests whether the MODIS BRDF parameters are applicable to characterize BRDF at a local scale of a Landsat TM pixel, or simply at a global scale. The results suggest that the MODIS BRDF parameters effectively characterize the BRDF of the Landsat imagery at a global average scale, but, at least in the Australian context, do not capture any further information about the BRDF of more local regions, or individual Landsat pixels.
Mathematizing the van Hiele levels: a fuzzy set approach

This paper deals with the relation of fuzzy sets and the van Hiele level theory of geometrical reasoning. It is a conceptual foundation of the van Hiele level theory based on non‐standard mathematical thinking. It attempts to mathematize the van Hiele levels of thinking, using fuzzy sets and fuzzy variables, and offers an insight into the approximation of the concept of state of a variable. The observed student profiles (overall states) of the acquisition of the van Hiele levels in Gutierrez, Jaime and Fortuny's alternative paradigm are characterized and analysed. This is accomplished by using fuzzy sets, fuzzy variables, probabilities and possibilities.
Neoclassical transport fluxes in the plateau regime in nonaxisymmetric toroidal plasmas

The neoclassical fluxes in the plateau regime in an arbitrary large aspect ratio nonaxisymmetric toroidal system are calculated using fluid equations. The results are evaluated explicitly for a stellarator and for a rippled tokamak. For typical stellarator parameters, the helical magnetic field contribution to the particle and heat fluxes is comparable to the toroidicity contribution, and therefore, cannot be neglected. In addition, the helical magnetic field contribution to the parallel viscosity is capable of reversing the directions of the bootstrap current and Ware pinch flux in the plateau regime. In contrast, the neoclassical particle and heat fluxes in a rippled tokamak are comparable to those in an axisymmetric tokamak after the radial electric field and parallel flow velocity are determined (without external sources).
Patterns and dynamics in transitional plane Couette flow

Near transition, plane Couette flow takes the form of large-scale, oblique, and statistically steady alternating bands of turbulent and laminar flow. Properties of these flows are investigated using direct numerical simulation in a tilted computational domain. Four regimes—uniform, intermittent, periodic, and localized—are characterized. The Fourier spectrum along the direction of variation of the pattern is presented, and the component corresponding to the pattern wavenumber is investigated as an order parameter. The mean flow of a periodic pattern is characterized and shown to lead to a relation between the Reynolds number and the wavelength and angle of a pattern.
On Solvability of Boundary Value Problem for Asymmetric Differential Equation Depending on x

Abstract We state the conditions of geometrical nature which guarantee the existence of a solution to the boundary value problem x ′′ + 2δx ′ + λf (x + ) − µg(x −) = h(t, x, x ′ ), x(0) = 0 = x(1) with a damping term 2δx ′ and nonnegative parameters λ, µ, provided that f (x +) − g(x −) is a sector-bounded nonlinearity.
PERMANENT DIPOLE CONTRIBUTION TO THE LINEAR ELECTRO-OPTIC EFFECT AND VALENCE BAND DISPERSION IN ZINC-BLENDE SEMICONDUCTORS

v,0, are significantly enhanced near band gap to the degree that simple bond-orbital theories, adequately describing nonresonant susceptibilities [2], can no longer be applied. The PE theories of Aronov and Pikus [3] and of Zhu and Chang [4] have considered a number of higher-order terms in the Luttinger Hamiltonian associated with the inversion asymmetry of zinc-blende (ZB) lattice, but their results were much too small in comparison with experimental observations [5]. In 1994 an approach combining bond-orbital dipole and Kane model adequately described the OR near the band gap [6]. In 1996 a heuristic approach, Hbf theory, had explained the unusually high native and field-induced anisotropies in the III-V multiple quantum wells [5]. Both theories looked at the changes caused by optical and /or electric fields (EF) on the shape and energy of the periodic part of the Bloch function that occur on the scale smaller than the Brillouin zone and are not accounted for in the Kane k ? p theory [7]. Here we show that important terms in PE and OR response of semiconductors, associated with permanent dipole moment (PDM) of some of the valence band (VB) states, cannot be accounted for, since they simply do not satisfy the Born‐von Karmann- (BvK) boundary conditions. Nevertheless, using the hybrid orbital basis in place of the more conventional S and P type states brings the inherent asymmetry of the bonding states into the Kane picture and adequately explains the origin and magnitude of OR and PE, the latter being the main object of interest.
Oblique propagation of electromagnetic and elastic waves for an array of cylindrical fibres

This paper presents analysis of electromagnetic and elastodynamic waves propagating through a doubly periodic array of cylindrical channels in oblique incidence. A new method, based on a multipole scattering approach, has been proposed to reduce these spectral problems for partial differential equations to certain algebraic problems of the Rayleigh type. We obtain a formulation in terms of an eigenvalue problem that enables us to construct the high‐order dispersion curves and to study both photonic and phononic band‐gap structures in oblique incidence. We also address the question of a singular perturbation induced by the conical incidence and discuss some effective properties for ferromagnetic photonic crystal fibres in the long‐wavelength limit.