Miracle-dz/UniFAR-FTUs huggingface dataset:
Natural convection boundary layer in a 5:1 cavity

The natural convection boundary layer in a tall cavity with an aspect ratio of AR=5 is studied numerically. The Rayleigh number based on the width of the cavity is RaW=4.028×108. The large eddy simulation method together with different subgrid scale models are used to study the near-wall behavior of the boundary layer and the turbulence structure. It is found that the dynamic subgrid scale model is the most accurate model in terms of predicting the transition location. Results also indicate that the conventional grid resolutions expressed in viscous units that are used for forced convection flows are not appropriate in the case of the natural convection flows and higher grid resolutions are necessary. The turbulence statistics are studied in both the turbulent and the transition regions. Although the results of the fully turbulent region show no important grid dependency, it is found that the accuracy of the results in the transition region is highly grid dependent, suggesting that the subgrid scale fluct.
Stability and instability of Liapunov-Schmidt and Hopf bifurcation for a free boundary problem arising in a tumor model

We consider a free boundary problem for a system of partial differential equations, which arises in a model of tumor growth. For any positive number R there exists a radially symmetric stationary solution with free boundary r = R. The system depends on a positive parameter μ, and for a sequence of values μ2 μ * , where μ * = μ2 if R > R and μ* R each of the stationary solutions which bifurcates from μ = μ2 is linearly stable if e > 0 and linearly unstable if e < 0. We also prove, for R < R, that the point μ = μ * is a Hopf bifurcation, in the sense that the linearized time-dependent problem has a family of solutions which are asymptotically periodic in t.
A GRAPH OF STATE CLASSES FOR FUZZY TIME PETRI NETS

Abstract The goal of this paper is to extend the state graph class concept of a time Petri net to the fuzzy state graph class concept of a Fuzzy Time Petri net (FTPN). The fuzzy state class graph is defined by focusing on: i) the fuzzy time domains associated to the state classes; ii) the update of the fuzzy time intervals after the firing of a transition; iii) the computation of Possibility and Necessity measures of transition firing.
Dispersive optical constants of amorphous Se1−xTex films

Optical constants of amorphous Se1−xTex films have been measured for 0⩽x⩽0.45 at wavelengths from 0.35 to 2 μm using both an ellipsometer and a spectrophotometer. The results show that the optical transmission cutoff wavelength, the refractive index, and the extinction coefficient vary linearly with x (the Te content). The optical constants are dispersive. The dispersion is attributed to the optical transition of electrons from the valence band to the conduction band. All results can be consistently explained on this basis. The substitution of Te atoms for Se atoms in Se1−xTex films increases the density and enhances the tailing of the localized states into the mobility gap, thus resulting in the change of optical constants with x in Se1−xTex films.
Aerodynamic test and analysis of a slender generic missile configuration

Abstract : This paper discusses the aerodynamic predictions, test , and analyses of a slender fin stabilized missile configuration at Mach numbers from 1.0 to 5. 0. Prediction techniques consisted of both empirical and analytical methods, including state-of-the-art computational fluid dynamic codes. Free flight tests were also conducted on subscale models to obtain an aerodynamic baseline to which the various predictions could be compared. This paper summarizes these results, attempts to identify the physics governing the flight trajectories, and proposes new ideas for further research in this technology area. Keywords: Free flight aerodynamics; Computational Fluid Dynamics; Supersonic; Static Dynamic Stability.
Inferences about the mean from censored water quality data

Several methods which are commonly used for making inferences about the levels of many metals and organic contaminants in ambient waters from type I censored data are critically evaluated, and their applications are illustrated using the concentrations of polychlorinated biphenyls in water samples from the Niagara River. Difficulties encountered in the application of all the methods, except the method of maximum likelihood, include ignoring the information available about the analytical detection limit and the unavailability of the standard errors for these estimates. Under the assumption that the distribution of the data is lognormal, the log regression method is modified to produce estimates of the censored values which use the detection limit information, and the properties of the maximum likelihood estimates for the lognormal mean are derived. Furthermore, an approximate confidence interval for the lognormal mean is given, and its use for estimating the load to and from the Niagara River is illustrated. The above methods along with a modification to the method of maximum likelihood are evaluated using Monte Carlo simulation.
Thermally activated magnetization reversal in submicron magnetic tunnel junctions for magnetoresistive random access memory

We have measured thermally activated magnetization reversal of the free layers in submicron magnetic tunnel junctions to be used for magnetoresistive random access memory. We applied magnetic field pulses to the bits with a pulse duration tp ranging from nanoseconds to 0.1 ms. We have measured the switching probability as a function of tp with a fixed field amplitude H, and as a function of H for fixed tp. For both cases, we find good agreement with the switching probability predicted by the Arrhenius–Neel theory for thermal activation over a single energy barrier.
Finite element analysis of electromagnetic torque saturation harmonics in a squirrel cage machine

The electromagnetic torque oscillations caused by saturation harmonics in a squirrel cage machine are analysed. Special attention is paid to the most important saturation harmonic of alternating field that has three times as many poles as fundamental harmonic and three times its frequency. The operations of the machine as a motor and as a self‐excited generator have been investigated. The 2D finite element time‐stepping method has been applied to the analysis of a particular machine performance. The finite element equations are coupled with circuits equations which describe the winding connections. The skew of the rotor slots is taken into account.
Measuring significant inhomogeneity and anisotropy in indoor convective air turbulence in the presence of 2D temperature gradient

Using a novel set up, experimental study of the statistical properties of a light beam propagating horizontally through indoor convective air turbulence in the presence of a 2D temperature gradient (TG) is presented. A laser beam enters a telescope from its back focal point by virtue of an optical fiber and is expanded and recollimated by it and then passes through the turbulent area. Then the beam enters another telescope’s aperture. A mask consisting of four similar widely separated small subapertures was installed in front of the second telescope’s aperture. The subapertures were equidistant from the optical axis of the telescope and located at the corners of a square. A flat plane heater is used to produce a vertical TG in the medium. Due to the limited width of the heater, a horizontal component for the TG appeared. Near the focal plane of the second telescope, four distinct images of the source are formed and recorded by a CCD camera. Due to the turbulence all the images (spots) in the successive frames fluctuate. Using the four spot displacements we have calculated the fluctuations of the angle of arrival (AA) over the subapertures. The statistical properties of the optical turbulence are investigated using variance analysis of the AA component fluctuations at horizontal and vertical directions over the subapertures for different temperatures of the heater at different heights of the beam path from the heater. Experimental results show that when the heater is turned off, the variances of horizontal and vertical components of the AA fluctuations are approximately equal to zero over all the subapertures. When it is turned on, the variance of the horizontal component of the AA fluctuations over all of the subapertures are larger than those from the vertical one. In addition, in this case, we find a significant dependence of the variance of the AA components on the height from the heater.
Multiscale Organization of Convection Simulated with Explicit Cloud Processes on an Aquaplanet

Abstract This study investigated the multiscale organization of tropical convection on an aquaplanet in a model experiment with a horizontal mesh size of 3.5 km (for a 10-day simulation) and 7 km (for a 40-day simulation). The numerical experiment used the nonhydrostatic icosahedral atmospheric model (NICAM) with explicit cloud physics. The simulation realistically reproduced multiscale cloud systems: eastward-propagating super cloud clusters (SCCs) contained westward-propagating cloud clusters (CCs). SCCs (CCs) had zonal sizes of several thousand (hundred) kilometers; typical propagation speed was 17 (10) m s−1. Smaller convective structures such as mesoscale cloud systems (MCs) of O(10 km) and cloud-scale elements ( 16 km) of O(100 km) area was also reproduced. Planetary-scale equatorial waves (with wavelengths of 10 000 and 40 000 km) had a major influence on the eastward propagation of the simulated SCC; destabilization east of the.
Observations of transverse ion acceleration in the topside auroral ionosphere

Data obtained from a sounding rocket flight which reached an apogee of 927 km and passed through several auroral arcs are reported. Thermal/superthermal ions were sampled by charged particle analyzers which allowed for a rapid (≈1 s) sampling of their distribution function. During portions of the flight when the rocket was not in an energetic auroral structure, the ion data are fit to a Maxwellian function which yields the plasma parameters. Throughout the middle portion of the flight when above 700 km altitude, ion distributions having a superthermal tail were measured. These ion distributions generally coexisted with a cold thermal core distribution and peaked at pitch angles slightly greater than 90°, which identifies them as conic distributions. These ions can be modeled using a bi-Maxwellian distribution function with a perpendicular (to B) temperature about 10 times greater than the parallel temperature of 0.15 eV. When the rocket was immersed in energetic auroral electron precipitation, two other ion distributions were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed continuously in these arcs. The characteristic perpendicular energy of the transversely bulk heated ions reached as high as 3 eV compared to typically less than 0.4 eV during nonauroral times. Cold ions flowing down the magnetic field were also continuously observed when the rocket was immersed in auroral electron precipitation and had downward speeds between 3 and 5 km/s. If one balances electric and collisional forces, these speeds translate to an electric field pointing into the atmosphere of magnitude 0.01 mV/m. A close correlation between auroral electron precipitation, measured electrostatic oxygen cyclotron waves, cold downflowing ions and transversely bulk heated ions will be shown. In addition, the ion distributions with a superthermal tail are seen to have a loose correlation with the aurora and measured H+ gyroharmonic wave structures. These observations are discussed in terms of some current theories of transverse ion energization.
Rates of change of the earth's magnetic field measured by recent analyses

The availability of accurate representations of the Earth's magnetic field for the past 25 years allows us to study the typical rates of change of the field as a function of the degree of the spherical harmonic. It is shown that there is a general increase in the relative rate of change as the degree of harmonic is increased. The analysis was only carried out to degree eight harmonics, because knowledge of the rate of change of the higher degrees is poor. If the projected rate of change continues in the same manner for higher degrees, then it is predicted that harmonics of, say, degree 14 will change at a rate of about 6% per year. This will mean that it should be easy to determine whether harmonics higher than degree fourteen originate in the core or whether they are caused by crustal magnetization. Although westward drift of the field does not necessarily tell us about motions of the core fluid at the core mantle boundary, it is probably true that these motions depend on the same parameters as those used to determine the westward drift. Since the westward drift depends on the longitudinal gradient of the component of field under consideration, it generally depends more on the higher orders of harmonic within each degree than on the lower orders, all other things being equal. In fact, not all other things are equal, because it is shown that in general the power in the higher orders of harmonic is less than the power in the lower orders. Another important factor in determining longitudinal motions is that it is the field at the core mantle boundary which is important, not the field at the Earth's surface. This results in the higher degrees being relatively more important than at the surface of the Earth. But because of the longitudinal differentiation, it turns out that in order to determine a major portion of the longitudinal drift it is necessary to have information about harmonics up to about degree 20. Therefore, with knowledge only of degrees eight or less, we really know rather little about longitudinal motions. Evidence for secular acceleration was found. Not surprisingly, the average rate of secular acceleration increased with the degree of harmonic, rising from 0.001°/yr2 for the dipole term to an average of 0.05°/yr2 for the degree eight harmonics.
Attractor dynamics of inflationary monomial potentials

We study the attractors solutions of the dynamical system of a scalar field endowed with monomial potentials of the form V(φ)∼φ2n. The evolution equations of the system are written as a dynamical system, and the critical points represent solutions of physical interest. It is easy to find curves that conect the critical points, some of which behave as attractor inflationary trajectories in phase space.
Nuclear Structure from a Simple Perspective

PART I: INTRODUCTION 1. Introduction 2. The Nuclear Landscape PART II: SHELL MODEL AND RESIDUAL INTERACTIONS 3. The Independent Particle Model 4. The Shell Model: Two-Particle Configurations 5. Multiparticle Configurations PART III: COLLECTIVITY, PHASE TRANSITIONS, DEFORMATION 6. Collective Excitations in even-even Nuclei: Vibrational and Rotational Motion 7. Evolution of Collectivity 8. The deformed Shell Model or Nilsson Model 9. Nilsson Model: Applications and Refinements 10. Microscopic Treatment of Collective Vibrations PART IV: EXPERIMENTAL TECHNIQUES 11. Exotic Nuclei and Radioactive Beams References Index
Direct construction of the galaxy luminosity function as a function of redshift

A novel method is proposed for investigating the evolution of the galaxy luminosity function using the results of faint galaxy redshift surveys. The luminosity function is calculated at a number of redshifts using the Phi(G) estimator of Felten (1976), and the errors on the luminosity function are estimated employing the spatial correlation function. While the standard method merely gives a yes/no decision about whether a particular model is an adequate fit to the data, the result of applying the new method is an immediate pictorial impression, as well as a direct quantitative measure, of both the strength and type of evolution and of the limitations of the data. This method is applied to three recent redshift surveys. There is strong evidence that the amplitude of the luminosity function increases by a large factor (about 3) in the redshift range 0-0.4. No evidence for any change in the shape of the luminosity function was found.
Direct-field electron acceleration with ultrafast radially polarized laser beams: scaling laws and optimization

In the past few years, there has been a growing interest for direct-field electron acceleration with ultra-intense and ultrafast radially polarized laser beams. This particular acceleration scheme offers the possibility of producing highly collimated mono-energetic relativistic attosecond electron pulses from an initial cloud of free electrons that could be produced by ionizing a nanoparticle. In this paper, we describe how electron energy scales with laser power and we explain how the beam waist size and the pulse duration can be optimized for maximal acceleration. The main conclusion of our work is that an electron can effectively reach the high-intensity optical cycles of this particular beam and be optimally accelerated without the necessity of being released by photoionization near the pulse peak.
AN ANALYSIS OF THE LATERAL HUNTING MOTION OF A TWO-AXLE RAILWAY WAGON BY DIGITAL SIMULATION

The article describes the results of studies which have been under way since 1961 and during which increasingly complex conditions similar to real situations were introduced progressively. It describes the mathematical model which was chosen for use on a digital computer. The results of this simulation tally with experimental results obtained, and the simulation is sufficiently precise to show what happens when a derailment occurs.
Disk Accretion Rates for T Tauri Stars

We present new measurements of disk accretion rates for T Tauri stars in the Taurus molecular cloud complex. Our results are based on intermediate-resolution spectrophotometry from 3200 to 5200 Å, which is used to derive the excess hot continuum emission produced by accretion onto the central star. Previous estimates of T Tauri accretion rates in the literature differ by as much as 1 order of magnitude; our measurements agree better with the lowest estimates, and we discuss the problems and systematic effects that led to the previous disagreement. In particular, we note that the stellar photospheric emission from nonaccreting T Tauri stars exhibits color anomalies compared to main-sequence stars; these anomalies make the estimated extinction depend upon the color index used. We argue that the V-R index is a reasonable compromise to match with optically derived spectral types, and that V-I and V-J are much more likely to be biased by cooler companion stars and starspots. We develop a calibration with which approximate mass accretion rates can be derived for T Tauri stars based on broadband photometry and spectral types, which should enable accretion rates to be estimated for large samples with greater ease.
Lateral Shifts in Near-Field Thermal Radiation with Surface Phonon Polaritons

It is well known that radiative heat transfer in the near field regime can be greatly enhanced because of photon tunneling, during which the classical radiation theory fails to predict the energy propagation direction. In the present article, we investigate the lateral shifts of energy pathways in near-field thermal radiation between two SiC plates separated by a vacuum gap. The energy streamline (ESL) method can be combined with fluctuational electrodynamics to trace the Poynting vector at a fixed parallel wavevector component β. The spectral energy flux exhibits nearly monochromatic enhancement with the excitation of surface phonon polaritons. In the spectral region important for radiative energy transfer, there exist considerable lateral shifts depending on the values of β. The range of β dominantly contributing to the spectral energy flux is identified for different wavelengths by examining the Poynting vector equation. With the use of ESLs, the effect of coupled surface polaritons on the lateral shift is also investigated. Furthermore, the lateral dimension for the SiC plates to be treated as infinitely extended is estimated based on the lateral shifts in the wavelength region that mostly contributes to the total energy flux.
Shallow‐water transmission loss prediction using the Biot sediment model

Experimental data and predicted propagation loss from three shallow‐water test sites with highly varied sediments are compared for frequencies from 25 to 800 Hz. The predicted loss was obtained using normal‐mode and adiabatic normal‐mode models with the sediment absorption calculated using the theory of Biot. The theory predicted a linear variation of absorption with frequency for a site off Corpus Christi, Texas, having a mud bottom (the mean grain size was 6.37 phi). The absorption was predicted to vary as frequency raised to the 1.76 power for a site off Daytona Beach, Florida having a medium‐to‐coarse sand bottom (the mean grain size was 0.85 phi). Range‐independent propagation was assumed for the sites just noted and the agreement between measured and predicted loss was good for frequencies from 100 to 600 Hz. Range‐dependent conditions existed for the third site, off the coast of Nova Scotia, where the sound‐speed profile, bottom sediments, and depth varied with range. Good agreement was obtained be.
Far-infrared observations and the structure of Wolf-Rayet ring nebulae

Detailed IRAS images of three WR ring nebulae, NGC 2359, RCW 58, and NGC 6888, are analyzed to obtain information on dust and associated gas masses within these nebulae, and these data are used together with kinematical data to derive the form and the structure of the nebulae. The IRAS maps show the presence of FIR emission that appears closely related to the optical shell structures. Calculations of forbidden line emission in the FIR associated with these nebulae suggest that only 8 to 20 percent of the observed FIR emission is due to these lines; the remaining emission is from heated dust. Dust temperatures are typically 33 K, although some high-temperature dust regions were found in the areas of greatest FIR emission. From continuum flux data, it was found that 0.25-1.3 solar mass is associated with the shells as dust, suggesting that their origins must be in the swept-up ISM near the WR stars, which has produced the ring nebulae. 33 refs.
Ion beam-induced anisotropic plastic deformation at 300 keV

Contrary to earlier predictions, ion irradiation at energies as low as 300 keV causes dramatic anisotropic plastic deformation of silica glass. Spherical colloidal silica particles with diameters of 125, 305, and 1030 nm were irradiated with Xe ions at energies in the range 0.3–4.0 MeV at temperatures between 85 and 380 K. Irradiation-induced anisotropic plastic deformation changes the colloid shape from spherical into oblate ellipsoidal at a rate that strongly increases with ion energy. At a fixed fluence, the transverse diameter increases with electronic energy loss. Even at an energy as low as 300 keV large particle anisotropy was found (size aspect ratio of 1.43 at 1×1015 cm−2). The transverse plastic strain gradually decreases with increasing irradiation temperature: it decreases by a factor 4.5 between 85 and 380 K. The data are in agreement with a viscoelastic thermal spike model for anisotropic deformation.