Miracle-dz/UniFAR-FTUs huggingface dataset:
Cancellation of singularities for synthetic aperture radar

In a basic model for synthetic aperture radar (SAR) imaging, one wishes to recover a function or distribution f from line integrals over circles whose centers lie on a given curve γ. In this paper, we consider the problem of recovering the singularities (wavefront set) of f given its SAR data, and specifically whether it is possible to choose a singular f whose singularities are hidden from γ, meaning that its SAR data is smooth. We show that f ʼs singularities can be hidden to leading order if a certain discrete reflection map is the identity, and give examples where this is the case. Finally, numerical experiments illustrate the hiding of singularities.
A Relationship between Loudness and the Minimum Perceptible Increment of Intensity

Using previously reported data (Phys. Rev., Vol. 31, May, 1928) concerning the differential intensity sensitivity of the ear, the number of perceptible increments of intensity is calculated as a function of the intensity expressed in db above the auditory threshold for frequencies of 200, 1000, 3000 and 10,000 c.p.s. These curves are then used in an attempt to arrive at a logical explanation of the data presented by Laird, Taylor and Wille (Jour. Acoustical Soc., Jan., 1932 “The Apparent Reduction in Loudness”).
The present state of digital vocoding technique: A diagnostic evaluation

Eight state-of-the-art pitch-excited digital vocoders (2400 bits/s) were evaluated with the Diagnostic Rhyme Test, a two-choice test of the discriminability of six elementary attributes of consonant phonemes. All of the systems tested performed adequately with respect to the attributes, voicing, nasality, sibilation, and compactness. None, however, permitted adequate discrimination of the attributes, sustention (friction versus plosion) and graveness. All systems reduced the gross discriminability of these attributes and significantly biased listeners perception of the states of one or both. It is hypothesized that these deficiencies stem primarily from inadequate spectrum sampling rate (i.e., frame rate) rather than inadequate "spectrum resolution. "
Improvement of Shape Factor and Loss of Surface Acoustic Wave Resonator Filter Composed of SiO2/High-Density-Electrode/LiTaO3

Radio frequency (RF) filters in high frequencies using surface acoustic waves (SAWs), such as MediaFLOTM, time division synchronous code division multiple access (TD-SCDMA) in China's handy phone system, and the global positioning system (GPS) in cars, require a narrow bandwidth. Thus, the SAW substrates for their RF filters also require an excellent temperature coefficient of frequency (TCF) and an optimum electromechanical coupling factor. The authors reported an RF SAW filter for MediaFLOTM using a shear horizontal (SH) leaky SAW (LSAW) on a flattened SiO2 film/high-density metal electrode/36–48°Y·X-LiTaO3 substrate. Although it had a good TCF and a large attenuation out of the pass band, it had a slightly large loss at the pass band only at room temperature compared with that of the conventional Al-electrode/42°Y·X-LiTaO3 in the previous report. In this study, calculation using the coupling-of-modes (COM) theory showed the effect of a new phase inverse method of obtaining a steep slope at the right side of the filter frequency characteristic, although the previous paper showed only the measured frequency characteristics. In addition, an RF SAW filter with a lower loss at the pass band and a better TCF than that of the previous report has been realized.
Building net-centric data strategies in support of a transformational MIW capability

The Mine Warfare (MIW) Community of Interest (COI) was established to develop data strategies in support of a future information-based architecture for naval MIW. As these strategies are developed and deployed, the ability for these datafocused efforts to enable technology insertion is becoming increasingly evident. This paper explores and provides concrete examples as to the ways in which these data strategies are supporting the technology insertion process for software-based systems and ultimately contribute to the establishment of an Open Business Model virtual environment. It is through the creation of such a collaborative research platform that a truly transformation MIW capability can be realized.
Large‐eddy simulation of roughness‐generated boundary‐layer noise

A computational study is carried out to predict rough‐wall boundary layer noise and elucidate noise generation mechanisms. As a first step, the sound radiation from a single hemispherical roughness element in a turbulent boundary layer at Reθ=7500 is investigated. The roughness height is 3.6% of the boundary layer thickness, or 95 wall units. The flow field is computed by large‐eddy simulation. The velocity statistics show reasonable agreement with the experimental data measured at Virginia Tech. Acoustic calculations are performed based on the Curle‐Powell integral solution to the Lighthill equation. The sound radiation is dominated by unsteady drag dipoles and their images in the wall, with the spanwise dipole of similar magnitude or stronger compared to the streamwise dipole. The viscous contribution to the drag dipole is negligible relative to the pressure contribution. Numerical experiments are performed to isolate the roles of vortex shedding and diffraction of convected hydrodynamic pressure by the.
Concentration field of multiple circular turbulent jets

The Reichardt hypothesis on the lateral transport of momentum has been used previously to predict the velocity field of multiple turbulent jets. In this paper, based on an extension of the Reichardt hypothesis to the lateral transport of pollutant, a method has been developed to predict the concentration field of multiple circular turbulent jets discharged into a large stagnant ambient. Experimental observations from one experiment with three parallel jets support the theoretical predictions.
Existence of time-dependent traffic equilibria

Time-dependent traffic equilibrium problem gorverned by quasimonotone cost functions are studied. We prove, under weak regularity assumptions, the existence of Wardrop equilibrium flows. Those results extend previous ones of [P. Daniele, A. Maugeri, and W. Oettli, Time-dependent traffic equilibria, J. Optim. Theory Appl. 103(3) (1999), pp. 543–555] and [A. Nagurney, D. Parkes, and P. Daniele, The internet, evolutionary variational inequalities, and the time-dependent braess paradox, Comput. Manag. Sci. 4 (2007), pp. 355–375] in which pseudomonotonicity of the cost function was assumed. They are based on reformulation of the traffic network problem in terms of variational inequalities or quasivariational inequalities. Nonelastic and elastic cases are considered.
Resonant absorption of Alfvenic surface waves and the heating of solar coronal loops

If irreversible heating of the solar corona is a result of hydromagnetic wave dissipation, then I propose that the relevant mode responsible for heating coronal active regions is an Alfvenic surface wave. Alfvenic surface waves are supported by the elasticity afforded by nonuniformities and therefore thrive in the inhomogeneous environment which characterizes coronal active regions.An Alfvenic surface wave is easily excited by the 300 s chromospheric oscillations shaking the footpoints of a magnetic loop (such loops are now thought to comprise coronal active regions); it travels along the loop's magnetic field lines and resonantly excites ''kinetic Alfven waves'' (KAW) within a thin (about 1 km thick) ''resonant absorption sheath'' which envelops the loop. Because of their kinetic structure, the resonantly excited KAW dissipate their energy very efficiently and thus act as an intermediary through which the Alfvenic surface wave irreversibly heats the sheath. Such a heated sheath induces a global convection within the loop: hot plasma rises in a boundary layer (< or approx. =100 km thick) adjacent to the sheath and enters the loop's interior (at the top of the loop) through the action of an electrostatic Rayleigh-Taylor instability. These upflows are aided by anomalous cross-field transport which resultsmore » from a temperature-gradient plasma instability within the boundary layer. Upon entering the loop's interior, this hot plasma cools by radiating in the EUV, condenses into clumps, and falls downward along the loop's field lines.If one assumes that the footpoints of a typical coronal loop (height approx. =10/sup 5/ km and poloidal radius approx. =10/sup 4/ km) are being shaken by 6 km s/sup -1/ chromospheric oscillations with a period of 300 s, energy balance results in a sheath temperature T/sub S/approx. =2.9 x 10/sup 6/ K and an interior temperature T/sub INT/approx. =1 x 10/sup 4/ K. The radiative output of such a loop is 6.8 x 10/sup 23/ ergs s/sup -1/. « less
Iterative learning control for nonlinear nonminimum phase plants with input disturbances

Learning control is a very effective approach for tracking control in processes occuring repetitively over a fixed interval of time. In the paper a robust learning algorithm is proposed for a generic family of nonlinear, nonminimum phase plants with input disturbances. The stable-inversion based learning controller for linear plants, as proposed by Gao and Chen (1998), is adapted to accomodate the above more general class of plants. The bounds on the asymptotic error for the learned input are exhibited via a concise proof. Simulation studies demonstrate that in the absence of input disturbances perfect tracking of the desired trajectory is achieved for nonlinear nonminimum phase plants. Further, in the presence of bounded random input disturbances, the tracking error converges to a neighborhood of zero. A bound on the tracking error is derived which is shown to grow continuously with a bound on the disturbances.
Effect of increased surface area of stainless steel substrates on the efficiency of dye-sensitized solar cells

In order to increase the electrical contact area between TiO2 particles and stainless steel (StSt) substrates of the dye-sensitized solar cells (DSSCs), StSt foil was roughened electrochemically using sulfuric acid with some additives. Compared with the DSSC with nontreated StSt substrate, DSSC with this roughened StSt substrate showed a 33% increase in light-to-electricity conversion efficiency with negligible effect on open circuit voltage (Voc) and fill factor. Electrochemical impedance spectroscopy clearly confirmed that the increased performance was due to a decreased electrical resistance at the TiO2/StSt interface.
Enhanced detection of NO2 with recessed AlGaN/GaN open gate structures

Recessing of the open gate region of AlGaN/GaN heterostructures is shown to dramatically enhance the sensitivity of these devices to surface interactions. This is demonstrated by NO2 exposure under humid conditions. NO2 adsorption at the open gate region leads to a decrease in two-dimensional electron gas conductivity, which we attribute to the interaction of NO2 with surface donor states. We find that the recessing enhances the sensitivity to NO2 by almost three orders of magnitude. This may also be used to improve the sensitivity of other (bio)chemical sensors based on AlGaN/GaN. Furthermore, the effect of humidity on the NO2 response is investigated.
Enhancement of Schottky barrier height on AlGaN/GaN heterostructure by oxidation annealing

The effect of preannealing of AlGaN under an oxygen ambient on the improvement of the Schottky barrier height on an AlGaN/GaN heterostructure was studied using synchrotron radiation photoemission spectroscopy. The oxidation annealing increased the Schottky barrier height from 0.59 to 0.84 eV, and dramatically reduced the reverse leakage current. The group-III elements (Ga, Al) outdiffused to the surface to form group-III oxides during the annealing, leaving group-III vacancies behind. The surface Fermi level shifted to the energy levels of group-III vacancies, leading to the enhancement of Schottky properties of AlGaN.
Bifurcations of a Nonlinear Small-Body Ocean-Mooring System Excited by Finite-Amplitude Waves

We investigate the response of a nonlinear small-body ocean-mooring system excited by finite-amplitude waves. The system is characterized by a coupled geometrically nonlinear restoring force defined by a single elastic tether. The nonlinear hydrodynamic exciting force includes both dissipative and convective terms that are not negligible in a finite wave amplitude environment. Stability of periodic motion is determined numerically and the bifurcation structure includes ultrasubharmonic and quasi-periodic response. The dissipation mechanism is found to control stability thresholds, whereas the convective nonlinearity governs the evolution to chaotic system response.
The use of Chebyshev cardinal functions for solution of the second‐order one‐dimensional telegraph equation

A numerical technique is presented for the solution of the second order one‐dimensional linear hyperbolic equation. This method uses the Chebyshev cardinal functions. The method consists of expanding the required approximate solution as the elements of Chebyshev cardinal functions. Using the operational matrix of derivative, the problem is reduced to a set of algebraic equations. Some numerical examples are included to demonstrate the validity and applicability of the technique. The method is easy to implement and produces very accurate results. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Near-infrared emission-line images of three Herbig-Haro objects

Flux-calibrated imagery in five emission-line and four narrow-band continuum filters are presented for three classical Herbig-Haro (HH) objects, HH 7-11, HH 12, and HH 34. 1.64 micron forbidden Fe II emission is detected in all three objects whose intensity is typically 20 percent. This line should be an excellent tracer of shocked ionized gas in highly obscured regions. Extinction appears to be unimportant in determining the morphology of these HH object systems. No near-IR continuum emission was detected from any of the HH objects, implying that these regions do not contain embedded stars. At positions where the flow terminates against a large obstacle, there are significant offsets between the shocked flow material and the shocked ambient medium. 39 refs.
Issues in applied structural equation modeling research

When using the popular structural equation modeling (SEM) methodology, the issues of sample size, method of parameter estimation, assessment of model fit, and capitalization on chance are of great importance in the process of evaluating the results of an empirical study. We focus first on implications of the large‐sample theory underlying applications of the methodology. The utility for applied contexts of the asymptotically distribution‐free parameter estimation and model testing method is discussed next. We then argue for wider use of a recently developed, non conventional model‐fit assessment strategy in SEM. We conclude by discussing the issue of capitalization on chance, primarily in situations in which exploratory and confirmatory analyses are conducted on the same data set.
Thermal conductivity probe: development of method and application to a coarse granular medium

The author describes the development of a probe method of measuring thermal conductivity k, to enable one to obtain k at times t before the linear domain of probe temperature against ln t is properly established. A variety of probe structures can be accommodated. A probe was constructed and the experimental procedure plus the associated analysis (using a simulation model PROBE) was verified by making measurements on materials of known properties. The technique was applied to an unconsolidated coarse granular medium, a pebble bed consisting of graded river pebbles with equivalent spherical particle diameters 24+or-7 mm, and a bed porosity of 0.396.
Numerical Study on Mass Transfer of a Vapor Bubble Rising in Very High Viscous Fluid

This study focused on a bubble rising behavior in a molten glass because it is important to improve the efficiency of removal of bubbles from the molten glass. On the other hand, it is expected that some gas species which exists in a bubble are transferred into the molten glass through the bubble interface, i.e., the mass transfer, subsequently, it may cause a bubble contraction in the molten glass. In this paper, in order to understand the bubble rising behavior with its contraction caused by the mass transfer through the bubble interface in the very high viscous fluid such as the molten glass, a bubble contraction model has been developed. The direct numerical simulations based on the MARS (Multi-interface Advection and Reconstruction Solver) coupled with the mass transfer equation and the bubble contraction model regarding the mass transfer from the rising bubble in very high viscous fluid have been performed. Here, the working fluids were water vapor as the gas species and the molten glass as the very.
Estimates for the Products of the Green Function and the Martin Kernel

Abstract Let Ω be a proper subdomain of ℝ n, n ≥ 2, and let x 0∈ Ω be fixed. By GΩ and KΩ we denote the Green function and the Martin kernel for Ω, respectively. Under a certain assumption on Ω near a boundary point ξ, we show that the product GΩ(x, x0)KΩ(x, ξ) is comparable to |x - ξ|2-n for x in a nontangential cone with vertex at ξ. We also give an estimate for the product KΩ(x, ξ)KΩ(x,η) in a uniform domain, where η is another boundary point.
Two-photon absorption in semiconductor saturable absorber mirrors

The nonlinear reflectivity of semiconductor saturable absorber mirrors has been investigated as a function of incident energy fluence. The presence of two-photon absorption in commonly used structures was confirmed via time-resolved differential reflectivity measurements. Theoretical calculations predict that two-photon absorption will expand the continuous-wave mode-locking stability regime against Q-switched mode-locking, yet may simultaneously induce multiple pulses in a laser cavity.
Characterization of Ion Cyclotron Resonance Acceleration for Electric Propulsion with Interferometery

This paper describes the experimental characterization of single-pass ion cyclotron resonance heating as applied to acceleration of ions for electric propulsion. A millimeter-wave interferometer system has shown to be a clear and simple method of quantifying ion acceleration due to ion cyclotron resonance heating. The experimental work was done on the VX-10 experiment of the variable specific impulse magnetoplasma rocket concept. The perpendicular velocity of the ions generated by ion cyclotron resonance heating was converted into axial velocity by the decreasing gradientoftheaxialmagnetic fieldattheexhaustofthepropulsionsystemfromconservationofthemagnetmoment. Thisincreaseinaxialvelocityispredictedtocauseadecreaseindensityduetoconservationofcurrentintheplasma. InterferometerdensitymeasurementsweretakenatthreedifferentlocationsontheVX-10experimentupstreamand downstream of the ion acceleration zone. A clear measurement of a 25% density drop for helium and a 40% density drop for deuterium was measured downstream of the ion resonance zone characteristic of ion acceleration.
On the Magnetic Properties of the Compound Mn_2As

The thermomagnetic properties of a compound Mn 2 As were investigated together with the phase diagram of Mn–As system. From the results of measurements of the temperature dependence of magnetic susceptibility and specific heat of the compound Mn 2 As, it was found that this alloy is antiferromagnetic with the Neel point at 573°K. The reciprocal of its susceptibility obeys the Curie-Weiss law in the high temperature range, but a considerable deviation therefrom can be seen just above the Neel point as in the case of ferrimagnetism. Based on the Curie constant obtained by the present experiment, the effective magneton number was calculated to be 5.2 per manganese ion. The total heat absorption due to the vanishing of antiferromagnetic order of spins in the present alloy was estimated to be 230 Cal/mol. A discussion based on the molecular field theory is given on the nature of the above-mentioned magnetic properties.
Optical CD metrology for directed self-assembly assisted contact hole shrink process

Simulations of Mueller matrix spectroscopic ellipsometry (MMSE) based scatterometry are used to predict sensitivity to dimensional changes and defects in directed self-assembly (DSA) patterned contact hole structures fabricated with phase-separated polystyrene-b-polymethylmethacrylate (PS-b-PMMA) before and after etch. The optical signature of Mueller matrix (MM) elements has a complex dependence on the structure topography and orientation, depolarization, and optical properties of the materials associated with the surface and any underlying layers. Moreover, the symmetry properties associated with MM elements provide an excellent means of measuring and understanding the topography of periodic nanostructures. A forward problem approach to scatterometry or optical model based simulations is used to investigate MMSE sensitivity to various DSA based contact hole structures and its limits to characterize DSA induced defects such as hole placement inaccuracy, missing vias, profile inaccuracy of the PMMA cylinder, and process induced defects such as presence of residual PMMA after etching.
Stellar metallicity distributions in local dwarf spheroidal galaxies: a comparison between model and observations

Abstract We analyze the main populations of 6 local Dwarf Spheroidal Galaxies by comparing the observed stellar metallicity distributions with the predictions of chemical evolution models. The predicted metallicity distributions of stars generally exhibit a low range of metallicities, a peak below the one of the MW disc in the solar neighborhood (but similar to the Halo), and a sharp decrease at higher metallicities in agreement with observations. The position of the peak is related to the low star formation rates adopted whereas the sharp decrease is a consequence of the occurrence of strong galactic winds. In the low metallicity tail of the distributions we predict a low number of stars in agreement with observations.
TAX AGGRESSIVENESS, LIFE CYCLE STAGES AND LEVEL OF INVESTMENTS: AN ANALYSIS OF THE MODERATING EFFECT ON B3 LISTED COMPANIES

The aim of present study was to analyze the moderating effect of the life cycle stages of firms (ECV) on the relationship between tax aggressiveness and the investment level of Brazilian companies listed in B3. The research descriptive, archival and quantitative approach used quarterly data of 2012-2020 of 3,853 observations of 270 companies available in the Thomson Reuters and COMDINHEIRO databases. The data were analyzed through descriptive statistics, differences tests, correlation analysis and regression with panel data using stata 16 software. The results showed that ECV have a moderating effect on relationship between tax aggressiveness and the investment level. It was observed that in companies in the Growth, Shakeout and Decline stages, tax aggressiveness has a positive effect on the level of investments, reinforcing the importance of tax planning. The results were consistent for different proxies of investment level and tax aggressiveness, including, using the tax burden measured from the Statement of Added Value (DVA). The findings provide important insights for accountants, managers, auditors and contribute to the discussion about the use of alternative proxies to identify tax aggressiveness and its impacts Brazilian context.