Miracle-dz/UniFAR-FTUs huggingface dataset:
A detailed X-ray and radio comparison of Kepler's supernova remnant

High-resolution radio images of Kepler's SNR (SNR (SN 1604) at 6 and 21 cm have been obtained using the VLA. The orientation of linear polarization in the SNR implies a substantial nonrandom radial component for the magnetic field of the remnant. Based on a new X-ray picture of the SNR, obtained using the Einstein Observatory, a detailed comparison of the X-ray and radio morphology is carried out. There is a good correlation between rotation measure, obtained from the radio maps, and emission measure, an X-ray-derived quantity in the SNR shell. From the mean electron density value infered from an analysis of X-ray fluxes, a mean radial magnetic field of 14 micro G and a total magnetic field of 70 microG are estimated. The energy density of relativistic electrons in Kepler's SNR in the shell comparable to the energy density in the magnetic field; the relativistic electron-pressure is 2 percent of the thermal gas pressure. The strong correlation between radio emissivity and X-ray emissivity found over the SNR in somewhat large scale can be ascribed to acceleration of thermal electrons at the shock wave and insignificant diffusion of resultant relativistic electrons.
On the Gamma-Ray Emission from 3C 279

Intense γ-ray emission was recently discovered from the direction of the quasar 3C 279 by the Compton GRO. It is proposed here that γ-rays are produced in the inelastic collisions of a mildly relativistic proton beam with matter of a thick accretion disk via decay of neutral pions and as a result of Comptonization of UV thermal photons by secondary electrons from decay of charged pions. The cone proton beam propagates along the axis of the disk funnel and illuminates its walls
Estimating Dependence of the Turbulent Length Scales on Model Resolution Based on A Priori Analysis

AbstractThe Reynolds-averaged Navier–Stokes simulation (RANS) and the large-eddy simulation (LES) have been widely used to parameterize unresolved turbulent motions for the atmospheric boundary layer. However, there is an intermediate model resolution, termed terra incognita, in which neither RANS nor LES is appropriate. Although identifying an appropriate turbulent length scale is essential for an eddy-diffusivity model, it is still uncertain how transition of the length scale is between the LES and RANS regimes. In the present study, dependence of the turbulent length scale on the horizontal resolution of a numerical model is investigated using a priori analysis for a convective boundary layer to explore a turbulent parameterization scheme applicable to the terra incognita region. Here, the approaches for estimating the length scales derived from the dissipation rate of the turbulent kinetic energy and the eddy viscosity are proposed. The estimated length scale depends on both the horizontal and vertica.
Local equilibrium and off-equilibrium thermoelectric effects in silicon semiconductors

Thermoelectric effects in bulk silicon are investigated by using a hydrodynamic model for the electron-phonon system, derived in the framework of extended thermodynamics. This model consists of a set of balance equations, where the higher order moments and the production terms are completely determined without any fitting procedure. If the system is in local thermal equilibrium, the thermopower and Peltier coefficients have been obtained and the phonon-drag contribution has been recovered. The model allows us to define and evaluate the Peltier coefficient when the system is out of thermal equilibrium.
An Observational Study of the Northern Hemisphere Wintertime Circulation

Abstract Twice-daily synoptic analyses are statistically analyzed for a sample of nine individual winters. Temporal variance and covariance quantities at each individual grid point are partitioned into “low-pass” (approximately 10–90 day) and “band-pass” (approximately 2.5–6 day) components by means of conventional filtering procedures. The time-filtered variance and covariance fields are displayed in terms of hemisphere maps. Included in the analysis are sea level pressure, 300 mb height, 500 mb wind statistics, and 850 mb temperature and poleward heat flux. The most definitive results of the study involve the “band-pass” fluctuations which appear to be associated with developing baroclinic waves. The fields of band-pass 1000, 50 and 300 mb geopotential height, as well as the 500 mb meridional wind component and relative vorticity all exhibit elongated variance maxima coincident with the two major Northern Hemisphere storm tracks, which lie downstream and somewhat poleward of the cores of the Asian and N.
Quantitative analysis of the sensitivity of porous silicon optical biosensors

The optical response of porous silicon affinity biosensors depends strongly on their nanomorphology because the sensing species does not completely fill the pores but is instead attached to the pore walls. The performance and sensitivity of porous silicon microcavity biosensors are calculated as a function of pore size using a simplified effective medium approximation. Excellent agreement is obtained between the model predictions and the experimental results after binding of aminopropyltriethoxysilane and glutaraldehyde in mesoporous and macroporous silicon microcavities. Detection of layers thinner than 0.01nm should be possible.
Variable selection in spatial regression via penalized least squares

We consider variable selection in linear regression of geostatistical data that arise often in environmental and ecological studies. A penalized least squares procedure is studied for simultaneous variable selection and parameter estimation. Various penalty functions are considered including smoothly clipped absolute deviation. Asymptotic properties of penalized least squares estimates, particularly the oracle properties, are established, under suitable regularity conditions imposed on a random field model for the error process. Moreover, computationally feasible algorithms are proposed for estimating regression coefficients and their standard errors. Finite‐sample properties of the proposed methods are investigated in a simulation study and comparison is made among different penalty functions. The methods are illustrated by an ecological dataset of landcover in Wisconsin. The Canadian Journal of Statistics 37: 607–624; 2009 © 2009 Statistical Society of Canada
Critical state models for flux‐pinning‐induced magnetostriction in type‐II superconductors

Models and calculated results are presented for the flux‐pinning‐induced magnetostriction in type‐II superconductors. Three models are considered for the critical state; the original Bean model, the Kim model, and the exponential model in which the critical current density is assumed to depend exponentially on the flux density. The analytic expressions of the length change under the magnetic field are derived for specimens having infinite slab geometry and under the assumption that the reversible part of the total magnetization is negligibly small. The results are used for computer simulations and the hysteresis loops are calculated over a wide range of the relevant parameters. Since the pinning‐induced magnetostriction reveals the pinning force directly, the hysteresis loops for each model have different features which are discussed in detail. It is also shown that the pinning force of the sample can be directly inferred from the width of the magnetostriction hysteresis loop. Finally, the experimental results on high‐temperature superconductors are discussed in comparison with the calculated results.
Acceleration of Maximum-Likelihood Image-Restoration for Fluorescence Microscopy and Other Noncoherent Imagery

In previous publications we presented an image-restoration algorithm for quantum-limited noncoherent imagery that is based on maximum-likelihood estimation [1]. This work was extended from the work of others in nuclear-medicine imaging [2,3]. A practical issue of using this method is in its speed of execution. This method is derived from the iterative expectation-maximization (EM) algorithm [4], and as such its convergence can be slow. We have observed this issue in our simulations as others have for positron-emission tomography [5].
A Numerical Model of Thermal Radiation in a Dusty Atmosphere

Abstract A method is presented for numerically calculating the infrared radiative fluxes in a dusty atmosphere: a multicomponent planar medium which absorbs, emits, and anisotropically scatters radiation. The method utilizes number of different solutions, depending on the particular monochromatic properties of the medium. The most general solution, including dust and gas absorption and dust scatter, is an iterative numerical integration of the system of simultaneous differential equations for the intensity. If scattering is relatively unimportant in a particular spectral region, the equations are uncoupled from one another and a non-iterative numerical integration is used. In spectral regions with very strong gaseous absorption, the optically thick limit is employed. Elsasser's band-averaged gas transmissivities are represented by a weighted sum of exponential functions of optical path. This model provides gas absorption coefficients which may be treated as constant over specified fractions of a band. The.
Estimation of Standard Errors of Empirical Bayes Estimators in Capm-Type Models

This paper is concerned with the problem of estimating the standard errors of the empirical Bayes estimators in linear regression models. The problem of deriving an exact expression for the standard error of this estimator is generally intractable. We suggest a procedure based on Efron’s bootstrap method as a way of estimating the standard error. It is shown, through simulations, that the bootstrap method provides a more accurate estimate of the standard error of the empirical Bayes estimator than the traditional large sample method.
Microbubble skin friction reduction on an axisymmetric body

A reduction in skin friction drag is shown when gas is introduced into the liquid turbulent boundary layer of a submerged axisymmetric body. The 89 mm diameter, 632 mm long body has a cylindrical balance 273 mm long. Free stream speeds in the 305 mm diameter tunnel are as high as 17 m/sec, giving length Reynolds number of up to 10 million. In general, skin friction reduction is shown to increase with increasing free stream speed. At high speeds, helium injection is shown to be more effective at reducing skin friction than is air injection. Maximum skin friction reduction is near 80%—a value in good agreement with the maximum value observed in the flat plate work of Madavan et al. [Phys. Fluids 27, 356 (1984)]. While maximum skin friction reduction was found at a free stream speed of 5 m/sec for the flat plate geometry, maximum skin friction reduction was at a free stream speed of 17 m/sec for the axisymmetric geometry.
Ultrasonic propagation, scattering, and defocusing in suspensions

Fine resolution narrow‐band pressure amplitude distribution measurements have been performed using a hydrophone in the field of a weakly focused bowl transducer radiating into castor oil and 1% and 2% by volume suspensions of 320‐μm polystyrene beads in castor oil over the frequency range 1.0 to 2.5 MHz at 20 °C. The axial distributions permitted determination of the excess attenuation due to scattering in the suspensions as a function of frequency. The frequency range included a resonance. The excess attenuation measured was compared with the theoretical predictions of Waterman and Truell [J. Math. Phys. 2, 512–537 (1961)] and good agreement was obtained. The values of the excess attenuation obtained were used to predict axial pressure amplitude distributions in the suspension. Although the excess attenuation was determined from far‐field measurements, the agreement between the predicted axial distributions and those measured experimentally extended well into the near field. Lateral distributions were measured at seven frequencies at the position of the geometrical center of curvature of the source and at the position of the true focus in the 1% suspension. Comparison with similar scans in castor oil alone revealed no detectable defocusing due to the presence of the scatterers.
Grating-based high energy X-ray interferometry with the Medipix-detector in simulation and measurement

In this paper we present the performance of the grating-based X-ray phase-contrast imaging approach using the photon counting Medipix-detector. This approach enables to extract information about the phase, the absorption, and the darkfield properties of the x-rayed object. We developed a complete simulation framework for a grating-based interferometer. This Framework incorporates all contributing physical aspects, especially the particle and the wave behaviour of the X-ray photons, realistic noise, and a detailed X-ray source and detector description. Furthermore, we present simulation results and compare them with measurements taken in our lab using a corresponding grating-based interferometer setup. We conclude that the results prove the correctness of our assumptions and simulation framework.
Phase-matched periodic electric-field-induced second-harmonic generation in optical fibers

Phase-matched electric-field-induced second-harmonic generation is demonstrated in single-mode germania-doped silica fibers. A periodic second-order nonlinearity is induced by a simple interdigitated electrode structure, which can be rotated to permit phase matching between all propagating modes. The most efficient mode interaction between HE11ω and HE112ω is achieved at 1.064 μm by using a Q-switched Nd+3:YAG laser. In principle, phase matching at any propagating wavelength is possible. This technique could be applied to planar as well as cylindrical waveguides and can be used with many non-χ(2) materials. The asymmetry in the applied electric field enhances the optical-field overlaps between modes of dissimilar orders, and this is also demonstrated. A conversion efficiency of 4.0 × 10−4% has been obtained in unoptimized devices. Device optimization is also discussed.
Symmetry Exploitation of Diffraction Gratings to Enhance the Spectral Resolution

A diffraction grating is a highly symmetric optical element with a physical structure that is invariant under translational spatial movements. The translational symmetry is reflected in the fields that are diffracted from the grating. Here, we introduce a plane-parallel mirror pair onto the grating, which translates the fields through double reflections, and we describe a method of exploiting the symmetry to enhance the spectral resolution of a diffraction grating beyond the limit that is set by the number of grooves. The mirror pair creates another virtual grating beside the original one, effectively doubling the number of grooves. Addition of more mirror pairs can further increase the effective number of grooves despite the increased complexity and difficulty of experimental implementation. We experimentally demonstrate the spectral linewidth reduction by a factor of four in a neon fluorescence spectrum. Even though the geometrical restriction on the mirror deployment limits our method to a certain range of the whole spectrum, as a practical application example, a bulky spectrometer that is nearly empty inside can be made compact without sacrificing the resolution.
Planning Tactile Recognition Paths in Two and Three Dimensions

A general problem in model-based object recognition is how the system should proceed when the available data are ambiguous (i.e., when either the object or its location in space are not uniquely identified), We show that this "best next view" problem can be solved for two-dimensional polygonal objects solely by touch. The solution is a low-order polynominal algorithm that in corporates uncertainty from the data-analysis level to the path-planning level. It has been tested both by simulation and by implementation on an experimental robot system. In three dimensions, the problem becomes inherently nonlinear and quite difficult. We describe the three-dimensional problem, discuss possible approaches, present a taxonomy that subsumes previous attempts, and display simulation results that describe the efficacy of our approach. We show that the heuristic of attempting to decompose the three-dimensional, four-degree-of-freedom, non linear problem into a pair of two-degree-of-freedom linear problems produces perfect paths about half of the time and is the most efficient complete decomposition method that has been implemented to date. 1. We can rotate and translate an arbitrary starting line so that it coincides with the x-axis, and transform the edges accordingly. 2. These bounds are derived from physical properties of the sensor, such as the angle at which it will skid off a smooth surface. 3. If the sets do not intersect, then there is no line that obeys the constraints and passes through both edges. 4. Some of the critical points in this example have the same α value, so there are fewer dashes marked on the a-axis than dots in the figure. 5. For typical sensor uncertainty values propagated through the interpre tation process, rotational uncertainty vastly dominates translational uncer tainty. Once rotational uncertainty is managed, translational uncertainty can usually be incorporated in a straightforward manner, by offsetting in the appropriate direction. 6. The reader is reminded that the coordinate system is located and oriented for convenience of calculation.
Effects of Linear Damping on Nonlinearly Coupled Waves

An investigation has been made of the influence of individual linear damping in a stable system of three resonantly interacting waves. Guided by the results from analog computations the exact analytic solution to the undamped system has been extended to cover the damped case by a generalization of the constants of motion. Computations show that the obtained solution gives a good approximation of the waves.
On the Role of Upper Tropospheric Jet Streaks and Leeside Cyclogenesis in the Development of Low-Level Jets in the Great Plains

Abstract A review of 15 cases of low-level jets (LLJ's) which developed in the Great Plains and which have been previously discussed in the literature is presented. The review notes that boundary-layer processes have been emphasized as causative factors in the development of the LLJ while upper tropospheric features were not considered and the importance of synoptic-scale processes was generally minimized. For 12 out of the 15 cases, a systematic upper level flow pattern is isolated which includes the existence of a trough over the southwest United States and the propagation of upper level jet streaks from the Rocky Mountains toward the Great Plains. This flow pattern is responsible for leeside cyclogenesis or leeside troughing that produces the pressure gradients needed for the development of LLJ'S. For the other three cases, a blocking ridge exists over the Great Plains and the upper level flow is relatively weak. It is during these situations that the “classic,” diurnally oscillating LLJ is observed. A.
Accuracy of mixed and control volume finite element approximations to Darcy velocity and related quantities

The accuracy of the Darcy velocity, flux, and stream function computed from lowest-order, triangle-based, control volume and mixed finite element approximations to the two-dimensional pressure equation is considered. The control volume finite element method, similar to integrated finite difference methods and analogous to the interpolation of Galerkin finite element results over “control volumes,” is shown to yield a conservative velocity field and smooth streamlines. The streamlines and fluxes through the system computed with the control volume finite element approach are compared to those computed from the mixed finite element method, which approximates the pressure and velocity variables separately. It is shown that for systems with only moderate degrees of heterogeneity, the control volume finite element method is the more computationally efficient alternative; i.e., it provides more accurate flow results for a given number of unknowns. For more variable or discontinuous permeability fields, by contrast, such as sand/shale systems, the mixed finite element method is shown to approximate flow variables more accurately and more realistically than the control volume method with the same number of unknowns.
Role of twin boundaries on vortex pinning of CSD YBCO nanocomposites

We study the effect of twin boundaries (TBs) on the critical current density of YBa2Cu3O 7 − x ? > (YBCO) films and nanocomposites grown on different substrates. Varying both the direction of the current and magnetic field, we show that the TB orientation is a crucial parameter to consider in the optimization of Jc for particular applications. A quantitative and detailed analysis of the role of TBs on vortex dynamics has allowed us to infer that extended TB planes in pristine YBCO films can reduce Jc by 60% at low temperatures due to vortex channeling effects or increase it by a 98% at high temperatures due to directional vortex pinning. Moreover, we demonstrate that TB length and distribution can be strongly modified in YBCO nanocomposites. We observe that TB planes with no vertical coherence are still effective for vortex pinning while are not to create channels for easy vortex flow.
A Fixed Point Approach to Stationary Heat Transfer in Electric Cables

Abstract In this paper we present a novel procedure for the determination of temperature in electric conductors. A Helmholtz-to-Poisson estimate is proved, that justifies to restrict the temperature dependence of the electrical resistivity to the conductor boundary. Hence we obtain a nonlinear potential problem for the relevant boundary temperatures, where the temperature dependence of the heat transfer coefficient is fully regarded. Using boundary integral operators, we represent the unknowns as the fixed point of a contraction. Finally a benchmark example is given in the rotationally symmetric case.