Miracle-dz/UniFAR-FTUs huggingface dataset:
Semi-insulating GaAs and Au Schottky barrier photodetectors for near-infrared detection (1280 nm)

Schottky barriers formed between metal (Au) and semiconductor (GaAs) can be used to detect photons with energy lower than the bandgap of the semiconductor. In this study, photodetectors based on Schottky barriers were fabricated and characterized for the detection of light at wavelength of 1280 nm. The device structure consists of three gold fingers with 1.75 mm long and separated by 0.95 mm, creating an E shape while the middle finger is disconnected from the outer frame. When the device is biased, electric field is stretched between the middle finger and the two outermost electrodes. The device was characterized by measuring the current-voltage (I-V) curve at room temperature. This showed low dark current on the order of 10-10 A, while the photocurrent was higher than the dark current by four orders of magnitude. The detectivity of the device at room temperature was extracted from the I-V curve and estimated to be on the order of 5.3x1010 cm.Hz0. 5/W at 5 V. The step response of the device was measured from time-resolved photocurrent curve at 5 V bias with multiple on/off cycles. From which the average recovery time was estimated to be 0.63 second when the photocurrent decreases by four orders of magnitude, and the average rise time was measured to be 0.897 second. Furthermore, the spectral response spectrum of the device exhibits a strong peak close to the optical communication wavelength (~1.3 μm), which is attributed to the internal photoemission of electrons above the Schottky barrier formed between Au and GaAs.
Transient Response of Supported Beams to Moving Forces with Sinusoidal Time Variation

Moving forces are a common loading pattern for flexible beams, found in many applications in both civil and mechanical engineering. These forces give rise to a transient response, the nature of which depends on the time variation of the amplitude of the force and its position along the beam. In addition to the possibility of numerical evaluation, closed form solutions of the beam response are beneficial for their simplicity of use, and because they allow an understanding of the system behavior. On the other hand, these prove to be rather complicated in most cases, and only a limited number of cases are available in the literature. This paper studies the simple but common case of a supported beam loaded by a force with sinusoidal time variation moving at a constant speed. Simple equations are presented for the approximated responses at and away from resonance, and their accuracy is discussed. Transient frequency response functions are also shown. Finally, as an example, the results are applied to an evaluation of the response of a beam footbridge to the action of a walker, and compared to code specifications.
Universal behavior of exchange-correlation energy in electron-hole liquid

Exchange-correlation energy of electron-hole liquid (EHL) is shown to be independent of different band characteristics of semiconductors. A simple expression of epsilon/sub xc/ for EHL in all semiconductors is given. In units of excitonic rydberg, epsilon/sub xc/ = (a+br/sub s/)/(c+dr/sub s/+r/sup 2//sub s/), where a = -4.8316, b = -5.0879, c = 0.0152, and d = 3.0426. Ground-state and thermodynamic properties calculated with this expression are in good agreement with earlier theoretical calculations and experimental results.
A surface remeshing technique for a Lagrangian description of 3D two‐fluid flow problems

Classical Lagrangian schemes applied to update the front position between two immiscible incompressible fluids have been long recognized to provide a sharp representation of the interface. However, the main drawback of these approaches is the progressive distortion in the distribution of the markers used to identify the material front. To avoid this problem, a 3D interface remeshing algorithm is proposed in this work. In addition, the remeshed front is enforced to preserve the global volume. These aspects are incorporated in an existing fluid dynamics formulation for the analysis of two‐fluid flows problems. The resulting formulation, called as the 3D‐moving Lagrangian interface remeshing technique, is applied in the numerical analysis of two‐fluid flow problems. Copyright © 2009 John Wiley & Sons, Ltd.
A discriminant space-based framework for scalable area-class mapping

Earlier research has introduced the concept of discriminant space, which is spanned by the covariates underlying area-class occurrences, for increased consistency, interpretability, and replicability in area-class mapping and uncertainty characterization. While simple univariate cases with b=1 (b being the dimension of the discriminant space) were investigated previously using simulated data, real world applications are usually multivariate with b>1, thus giving rises to the need for developing discriminant models in spaces of higher dimensionality for increased applicability. This paper describes combined use of generalized linear modeling and kriging for area-class mapping, with the former deterministically predicting mean class responses while the latter making use of spatially correlated residuals in the predictive class models. Scalability in area-class mapping is facilitated by flexible implementation of scale-dependent prediction of mean class responses and point- vs. area-support kriging of the residuals. This is followed by an empirical study concerning land cover mapping in central western Montana, which confirmed the effectiveness of the proposed strategy combining regression and kriging for scale-dependent mapping of area classes.
HYDRODYNAMIC FORCES ON A VERTICAL CYLINDER IN CURRENT AND WAVES

A vertical cylinder in uniform current and regular waves is analysed based on potential flow theory and low current speed approximation. The perturbation theory is formulated by expanding the velocity potential in a power series of current speed U and by neglecting the terms of order O (U2). This reduces the boundary-value problem to the integral equation, whose kernel functions involve only the Green's function with zero current speed. The solutions are derived in explicit form for the first-order wave exciting force, mean wave drift force and wave drift damping force on the cylinder, where the nonlinear coupling between the steady and unsteady potentials at the free surface is taken into account. Numerical results are also presented, which lead to the following conclusions : i) The hydrodynamic forces on the vertical cylinder in current and waves are significantly influenced by the presence of current.ii) The wave drift force is more sensitive to current than the first-order wave exciting force. With the increase of current speed in the wave propagation direction, the mean drift force tends to increase compared with the force without current.iii) The nonlinear coupling between the steady and unsteady potentials at the free surface has a significant effect on the hydrodynamic forces, in particular on the wave drift force and wave drift damping. The inclusion of these effects results in an increase of the wave drift damping coefficient by one or two times the value predicted with the classical free surface condition.
DIRECT AND INVERSE SOLUTIONS OF GEODESICS ON THE ELLIPSOID WITH APPLICATION OF NESTED EQUATIONS

AbstractThis paper gives compact formulae for the direct and inverse solutions of geodesics of any length. Existing formulae have been recast for efficient programming to conserve space and reduce execution time. The main feature of the new formulae is the use of nested equations for elliptic terms. Both solutions are iterative.
Automatic keratometry in slit lamps

We have developed an automatic keratometer module for slit lamp that provides automatic measurements of the radii of the corneal curvature. The system projects 72 light spots displayed in a precise circle at the examined cornea. The displacement and deformation of the reflected image of these light spots are analyzed providing the keratometry. Measurements in the range of 26,8D - 75D can be obtained and a self-calibration system has been specially designed in order to keep the system calibrated. Infrared leds indicate automatically which eye is being examined. Volunteer patients (492) have been submitted to the system and the results show that our system has a high correlation factor with the commercially available manual keratometers and the keratometry measurements from a topographer. Our developed system is 95% in agreement with the corneal topographer (Humphrey - Atlas 995 CZM) and the manual keratometer (Topcon OM-4). The system's nominal precision is 0,05mm for the radii of curvature and 1o for the associated axis.
New piezoelectric crystal: Synthetic fresnoite (Ba2Si2TiO8)

A fresnoite (Ba2Si2TiO8) single crystal was grown from the melt by the Czochralski method. Synthetic fresnoite has an electromechanical coupling factor in the thickness shear mode of k15=0.28, and a resonance‐frequency temperature coefficient in this mode of Tfr=−33 ppm/°C. Fresnoite is considered to be superior to Ba2Ge2TiO8 for various piezoelectric applications because of the absence of microtwins observed in Ba2Ge2TiO8.
Transverse vibrations of shear-deformable beams using a general higher order theory

Abstract A new one-dimensional theory is presented for studying the static and vibration behavior of cylindrical or prismatic beam-type structures. This general higher order theory, which is developed for beams having an arbitrary cross-section, accurately accounts for transverse shear deformation out of the cross-sectional plane and anticlastic-type deformation within the cross-sectional plane. The two equations of motion are derived using Hamilton's principle along with the full three-dimensional constitutive relations. The resulting equations correctly predict the stress-free conditions on the beam cylindrical surface. A simplified form of the general higher order theory is also presented that accounts for transverse shear-dependent deformation out of the cross-sectional plane, but assumes that the stresses within the cross-section are zero. Both approaches are shown exactly to reduce to existing first and higher order theories for beams with thin rectangular cross-sections. Numerical results show that including in-plane cross-sectional deformations will slightly increase the bending-dominant frequency and greatly reduce the shear-dominant frequency for extremely short wavelengths. Furthermore, the cross-section aspect ratio has only a minimal effect on the bending-dominated frequency, even for short wavelengths, but the effect on the shear-dominated frequency can be significant for long slender beams with either rectangular or an elliptical cross-section.
Nonlinear waveform tomography applied to crosshole seismic data

The acoustic inverse problem of crosshole seismology is nonlinear in the medium velocities and ill‐posed because of the lack of complete data coverage surrounding the area of interest. In light of these facts, this paper develops a new nonlinear waveform tomography technique for imaging acoustic velocities from crosshole seismic data. The technique, based on Tikhonov regularization, defines solution models that minimize the normed misfit between observed and modeled data subject to a constraint on the spatial roughness of the model. This type of regularization produces minimum structure velocity models which can vary in their degree of smoothness versus fit to the data. We solve the Tikhonov minimization condition numerically using a conjugate gradient algorithm. To accurately calculate the components of the forward problem, we use a frequency‐domain integral equation method with sinc basis functions. The integral equation method discretizes the integral form of the acoustic wave equation over a 2-D area .
Flow, flow shear, and related profiles in helicon plasmas

Measurements of the three-dimensional ion flow field and the ion temperature in a cross section of a cylindrical, argon, helicon plasma are presented. When these measurements are combined with radially resolved measurements of the plasma density, electron temperature, neutral density, and neutral temperature, the radial profiles of the ion viscosity and ion-neutral momentum transfer rate can be calculated. The ion viscosity and ion-neutral momentum transfer rate profiles are important input parameters for theoretical models of azimuthal flows arising from the nonlinear interaction of drift waves in helicon sources. The experimentally determined magnitudes and radial profiles reported in this work are significantly different than those used in recent theoretical studies. Measurements of the radial flow of argon neutrals and helium neutrals are also presented for a helicon plasma.
A Khovanov stable homotopy type

Given a link diagram L we construct spectra X j Kh ( L ) so that the Khovanov homology Kh i,j ( L ) is isomorphic to the (reduced) singular cohomology H i ( X j Kh ( L )). The construction of X j Kh ( L ) is combinatorial and explicit. We prove that the stable homotopy type of X j Kh ( L ) depends only on the isotopy class of the corresponding link.
The Absorption of Sound by Small Areas of Absorbing Material

An indirect experimental check is now obtained for the calculated “shape factor” for an absorbing strip of material in a reflecting wall, reported previously The effect of the strip on each of the component “partial waves” in the incident plane wave is studied by placing the strip in a special enclosure, the shape of which allows the partial waves to be studied individually as isolated normal modes of vibration. A semicylindrical room is employed; its concave wall tends to “focus” sound upon the center of the opposite, flat wall on which the absorbing panel is centered. If the wave equation is set up in elliptic cylinder coordinates with the edges of the panel as foci, the boundary conditions are readily satisfied. The theory is strictly applicable to a semielliptical room only, but holds well in the semicircular for strip widths up to one‐third the diameter. The experimental enclosure has a 14‐inch radius, a “thickness” of 4 inches between the parallel walls, and is constructed with highly reflective metal surfaces. The selective damping of various normal modes is investigated for strip widths from about one to ten inches, for several values of normal acoustic impedance. The results substantiate the calculated values of “shape factor” which were given in the previous paper.
Analytical solution of a condenser microphone model as an example of the mathematical treatment of coupled acoustic systems

In this work an analytical model for a condenser microphone with a pattern of holes in the electrode is solved approximately by applying an operator method of quantum mechanics. Essential is the replacement of the operators corresponding to the Green’s functions of the cylinder in the fundamental integral equations of the system by products of identity operators times an appropriately chosen constant. The second approximation is the averaging of the holes and by replacing the effect of the holes in the electrode by a product of the identity operator times the part of the area of the small holes in the electrode compared to the whole area of the electrode. The last approximation is the replacement of the displacement of the fluid in the small holes by their mean value and the assumption of small holes compared to the total area of the electrode. By a summation method over zeros of Bessel functions it is possible to do infinite summations exactly and to provide an analytical solution of the average displace.
Void distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part II: numerical simulation

Numerical simulations of bubbly flows in a four by four rod bundle are carried out using a multi-fluid model to examine effects of the numerical treatment of phase distribution and drag model. The transport equations of bubble number density and void fraction are used as the continuity equation of the gas phase. Two drag models are tested: one of them accounts for the bubble deformation (aspect ratio), whereas the other does not. The rod diameter, the rod pitch and the hydraulic diameter of the rod bundle are 10, 12.5 and 9.1 mm, respectively. The gas and liquid volume fluxes are JG = 0.06 m/s and JL = 0.9 and 1.5 m/s, respectively. The bubble diameter ranges from 1 to 5 mm. Comparisons between the numerical and measured data show that (1) the restriction on bubble lateral motion due to the presence of rods can be taken into account by using the transport equation of bubble number density, whereas that of the void fraction cannot deal with the restriction and causes large errors in the distribution of void fraction and (2) the reduction in the bubble-relative velocity near the wall is predictable by using the drag model accounting for the bubble deformation effect.
Which magnetic storms produce relativistic electrons at geosynchronous orbit

Relativistic electrons appear in the geosynchronous environment following some, but not all, geomagnetic storms. The ability to identify which storms produce these electrons would bring us much closer to explaining the mechanism responsible for their appearance, and it would provide the space weather community with a means to anticipate the electron hazard to geosynchronous spacecraft. We apply a recently developed statistical technique to produce an hourly time series of relativistic electron conditions at local noon along geosynchronous orbit using several geosynchronous monitors. We use a cross-correlation analysis to determine what parameters in the solar wind and magnetosphere might influence the flux of relativistic electrons. We then perform a superposed epoch analysis to compare storms with and storms without the appearance of these electrons. We investigate a number of solar wind and magnetospheric parameters for these two sets of storms at 1-hour resolution. In particular, sustained solar wind velocity in excess of 450 km s−1 is a strong external indicator of the subsequent appearance of relativistic electrons. In the magnetosphere, long-duration elevated Pc 5 ULF wave power during the recovery phase of magnetic storms appears to discriminate best between those storms that do and do not produce relativistic electrons.
Tilted fiber Bragg grating sensors

Optical fiber gratings have developed into a mature technology with a wide range of applications in various areas, including physical sensing for temperature, strain, acoustic waves and pressure. All of these applications rely on the perturbation of the period or refractive index of a grating inscribed in the fiber core as a transducing mechanism between a quantity to be measured and the optical spectral response of the fiber grating. This paper presents a relatively recent variant of the fiber grating concept, whereby a small tilt of the grating fringes causes coupling of the optical power from the core mode into a multitude of cladding modes, each with its own wavevector and mode field shape. The main consequence of doing so is that the differential response of the modes can then be used to multiply the sensing modalities available for a single fiber grating and also to increase the sensor resolution by taking advantage of the large amount of data available. In particular, the temperature cross‐sensitivity and power source fluctuation noise inherent in all fiber grating designs can be completely eliminated by referencing all the spectral measurements to the wavelength and power level of the core mode back‐reflection. The mode resonances have a quality factor of 105, and they can be observed in reflection or transmission. A thorough review of experimental and theoretical results will show that tilted fiber Bragg gratings can be used for high resolution refractometry, surface plasmon resonance applications, and multiparameter physical sensing (strain, vibration, curvature, and temperature).
Lineshape estimation for magnetic resonance spectroscopy (MRS) signals: self-deconvolution revisited

Magnetic resonance spectroscopy (MRS) is an effective diagnostic technique for monitoring biochemical changes in an organism. The lineshape of MRS signals can deviate from the theoretical Lorentzian lineshape due to inhomogeneities of the magnetic field applied to patients and to tissue heterogeneity. We call this deviation a distortion and study the self-deconvolution method for automatic estimation of the unknown lineshape distortion. The method is embedded within a time-domain metabolite quantitation algorithm for short-echo-time MRS signals. Monte Carlo simulations are used to analyze whether estimation of the unknown lineshape can improve the overall quantitation result. We use a signal with eight metabolic components inspired by typical MRS signals from healthy human brain and allocate special attention to the step of denoising and spike removal in the self-deconvolution technique. To this end, we compare several modeling techniques, based on complex damped exponentials, splines and wavelets. Our results show that self-deconvolution performs well, provided that some unavoidable hyper-parameters of the denoising methods are well chosen. Comparison of the first and last iterations shows an improvement when considering iterations instead of a single step of self-deconvolution.
ORIGIN OF CORONAL SHOCK WAVES ASSOCIATED WITH SLOW CORONAL MASS EJECTIONS

We present a multiwavelength study of five coronal mass ejection/flare events (CME/flare) and associated coronal shock waves manifested as type II radio bursts. The study is focused on the events in which the flare energy release, and not the associated CME, is the most probable source of the shock wave. Therefore, we selected events associated with rather slow CMEs (reported mean velocity below 500 km s−1). To ensure minimal projection effects, only events related to flares situated close to the solar limb were included in the study. We used radio dynamic spectra, positions of radio sources observed by the Nançay Radioheliograph, GOES soft X-ray flux measurements, Large Angle Spectroscopic Coronagraph, and Extreme-ultraviolet Imaging Telescope observations. The kinematics of the shock wave signatures, type II radio bursts, were analyzed and compared with the flare evolution and the CME kinematics. We found that the velocities of the shock waves were significantly higher, up to one order of magnitude, than the contemporaneous CME velocities. On the other hand, shock waves were closely temporally associated with the flare energy release that was very impulsive in all events. This suggests that the impulsive increase of the pressure in the flare was the source of the shock wave. In four events the shock wave was most probably flare-generated, and in one event results were inconclusive due to a very close temporal synchronization of the CME, flare, and shock.