Miracle-dz/UniFAR-FTUs huggingface dataset:
Circulation and formation number of laminar vortex rings

The formation time scale of axisymmetric vortex rings is studied numerically for relatively long discharge times. Experimental findings on the existence and universality of a formation time scale, referred to as the ‘formation number’, are confirmed. The formation number is indicative of the time at which a vortex ring acquires its maximal circulation. For vortex rings generated by impulsive motion of a piston, the formation number was found to be approximately four, in very good agreement with experimental results. Numerical extensions of the experimental study to other cases, including cases with thick shear layers, show that the scaled circulation of the pinched-off vortex is relatively insensitive to the details of the formation process, such as the velocity programme, velocity profile, vortex generator geometry and the Reynolds number. This finding might also indicate that the properly scaled circulation of steady vortex rings varies very little. The formation number does depend on the velocity profile. Non-impulsive velocity programmes slightly increase the formation number, while non-uniform velocity profiles may decrease it significantly. In the case of a parabolic velocity profile of the discharged flow, for example, the formation number decreases by a factor as large as four. These findings indicate that a major source of the experimentally found small variations in the formation number is the different evolution of the velocity profile of the discharged flow.
Rotationally driven interchange instability: Reply to André and Ferrière

[1] We derive the dispersion relation for the rotationally driven interchange instability, using the same basic equations as in our previous work (Vasyliūnas, 1994; Pontius, 1997) but taking care to keep the terms we had overlooked (as pointed out by Andre and Ferriere (2007)), and show that inclusion of the Coriolis force does modify the dispersion relation, reducing the growth rate of the instability and adding an oscillating component. Its effect becomes negligible only in the limit of azimuthal wavelength very short in comparison to radial distance, in the limit of plasma acceleration time very short in comparison to rotation period, and in the singular case of flux tube content proportional to equatorial field strength. Andre and Feriere (2007) find no effect of the Coriolis force because they assume all wavelengths to be short. For plasma acceleration time longer than the rotation period, the effect of the Coriolis force can restrict the range of radial gradients that are unstable. Although not a generally valid result, neglect of the Coriolis force effects is in practice applicable as long as the fastest-growing (hence presumably the most significant) instabilities are those with very short wavelengths.
Washington photometry of five star clusters in the Large Magellanic Cloud

Abstract We present CCD photometry in the Washington-system C and T1 passbands down to T1 ~ 22.5 mag in the fields of NGC 1697, SL 133, NGC 1997, SL 663, and OHSC 28, five mostly unstudied star clusters in the LMC. Cluster radii were estimated from star counts in appropriately sized boxes distributed throughout the entire observed fields. We perform a detailed analysis of field-star contamination and derive cluster colour–magnitude diagrams (CMDs). Based on the best fits of isochrones computed by the Padova group to the (C − T1, T1) CMDs, the δ(T1) index and the ‘standard giant-branch’ procedure, we derive metallicities and ages for the five clusters. With the exception of NGC 1697 (age = 0.7 Gyr, [Fe/H] = 0.0 dex), the remaining four clusters are of intermediate age (from 2.2 to 3.0 Gyr) and relatively metal poor ([Fe/H] = −0.7 dex). We combine our sample with clusters with ages and metallicities on a similar scale and examine relationships between position in the LMC, age and metallicity. We confirm previous results that clusters younger than ~ 1 Gyr were formed during an outside-in process; this occurred after a burst of cluster formation that took place mainly in the outer disk and peaked ~ 2 Gyr ago. Finally, the cluster and field age–metallicity relations (AMRs) show evidence for a metallicity offset but do overlap, particularly on the upper-envelope side of the cluster AMR.
On the Far-Infrared Emission of Quasars

Infrared spectral energy distributions between 4.8 and 200 μm are presented for a subsample of 10 quasars and radio galaxies from the European Central Quasar Programme observed with the Infrared Space Observatory. For three of the sources, this represents the first far-infrared detection. The spectral energy distributions (SEDs) reveal signatures of thermal dust as well as synchrotron emission. In most cases, one of the two components is so dominant that the other remains hidden. The SEDs of the radio-quiet and steep-spectrum quasars show a bump around 60 μm and a decline longward of 100 μm—strong evidence for thermal emission. It can be described as a superposition of several modified blackbodies, showing the broad variety of temperatures from hot (≈ 600 K) to cool (≈ 30 K) dust present in these objects. The infrared emission of the flat-spectrum radio quasars is in smooth continuation of the radio spectrum, supporting the interpretation as synchrotron emission. For one of these sources (3C 279), a bump is prying above the synchrotron spectrum, and we interpret it as thermal emission. For comparison within the framework of unified schemes, the radio galaxies Cyg A (3C 405) and 3C 20 are observed. While 3C 20 has not been detected, Cyg A reveals an infrared spectrum surprisingly similar to that of 3C 48 and the radio-quiet quasars, which strongly supports the interpretation of the radio galaxy Cyg A as a hidden quasar.
A note on the design of homogeneous time-varying stabilizing control laws for driftless controllable systems via oscillatory approximation of Lie brackets in closed-loop

A constructive method for time-varying stabilization of smooth driftless controllable systems is developed. It provides time-varying homogeneous feedback laws that are continuous and smooth away from the origin. These feedbacks make the closed-loop system globally exponentially asymptotically stable if the control system is homogeneous with respect to a family of dilations, and, using local homogeneous approximation of control systems, locally exponentially asymptotically stable otherwise. The method uses some known algorithms that construct oscillatory control inputs to approximate motion in the direction of iterated Lie brackets, that we adapt to the closed-loop context.
Evolution of enstrophy in shock/homogeneous turbulence interaction

Abstract Interaction of turbulent fluctuations with a shock wave plays an important role in many high-speed flow applications. This paper studies the amplification of enstrophy, defined as mean-square fluctuating vorticity, in homogeneous isotropic turbulence passing through a normal shock. Linearized Navier–Stokes equations written in a frame of reference attached to the unsteady shock wave are used to derive transport equations for the vorticity components. These are combined to obtain an equation that describes the evolution of enstrophy across a time-averaged shock wave. A budget of the enstrophy equation computed using results from linear interaction analysis and data from direct numerical simulations identifies the dominant physical mechanisms in the flow. Production due to mean flow compression and baroclinic torques are found to be the major contributors to the enstrophy amplification. Closure approximations are proposed for the unclosed correlations in the production and baroclinic source terms. The resulting model equation is integrated to obtain the enstrophy jump across a shock for a range of upstream Mach numbers. The model predictions are compared with linear theory results for varying levels of vortical and entropic fluctuations in the upstream flow. The enstrophy model is then cast in the form of $k$ – $\epsilon $ equations and used to compute the interaction of homogeneous isotropic turbulence with normal shocks. The results are compared with available data from direct numerical simulations. The equations are further used to propose a model for the amplification of turbulent viscosity across a shock, which is then applied to a canonical shock–boundary layer interaction. It is shown that the current model is a significant improvement over existing models, both for homogeneous isotropic turbulence and in the case of complex high-speed flows with shock waves.
BUDGET OF ANGULAR MOMENTUM AND ENERGY IN TROPICAL CYCLONES

Abstract The surface stress in tropical storms is computed as a function of the radius, from mean wind data in the troposphere. If only the symmetrical part of the circulation is considered, the stress ranges from 1 dyne per square centimeter in the outskirts to 20 dy/cm2 at a distance of 1 degree latitude from the center. Inclusion of the mean asymmetry of the wind field, resulting from superposition of steering current and vortex, yields values about 20 per cent higher. The absolute angular momentum budget shows that most net inward momentum transport is carried by the symmetrical part of the circulation near the core, and that the asymmetrical part contributes up to 50 per cent at a distance of 6 deg lat from the center. Calculation of the angular momentum transport due to the earth's rotation in inflow and outflow layers shows that the vertical momentum transport is directed upward everywhere; outside the 2-deg radius, this transport is accomplished by eddies. Generation and dissipation of kinetic ene.
Hybrid atomistic simulation methods for materials systems

We review recent progress in the methodology of hybrid quantum/classical (QM/MM) atomistic simulations for solid-state systems, from the earliest reports in 1993 up to the latest results. A unified terminology is defined into which the various and disparate schemes fit, based on whether the information from the QM and MM calculations is combined at the level of energies or forces. We discuss the pertinent issues for achieving ‘seamless’ coupling, the advantages and disadvantages of the proposed schemes and summarize the applications and scientific results that have been obtained to date.
Co/sup 60/ gamma ray and electron displacement damage studies of semiconductors

A general method for relating Co/sup 60/ gamma ray and monoenergetic electron beam displacement damage is presented. The approach is based on the concept of effective "displacement damage dose", which is analogous to ideas used to study ionizing radiation effects. The response to electron damage of p-type gallium arsenide and indium phosphide solar cells, as previously reported for p-type silicon solar cells, is proportional to the square of the nonionizing energy loss. >
Inference for Autocorrelations under Weak Assumptions

Abstract In this article we consider the large-sample behavior of estimates of autocorrelations and autoregressive moving average (ARMA) coefficients, as well as their distributions, under weak conditions. Specifically, the usual text book formulas for variances of these estimates are based on strong assumptions and should not be routinely applied without careful consideration. Such is the case when the time series follows an ARMA process with uncorrelated innovations that may not be assumed to be independent and identically distributed. As a specific case, it is well known that if the process is independent and identically distributed, then the sample autocorrelation estimates, scaled by the square root of the sample size, are asymptotically standard normal. This result is used extensively as a diagnostic check on the residuals of a fitted model, or as an initial test on the observed time series to determine whether further model fitting is warranted. In this article we show that this result can be quite.
A Model of Turbulent Burning Velocity Taking the Preferential Diffusion Effect into Consideration

In our previous work, we found that the preferential diffusion in a turbulent flame played an important role in its turbulent combustion characteristics, and estimated the local burning velocity in premixed turbulent combustion experimentally, taking account of the preferential diffusion effect. In this study, a model, which takes the preferential diffusion effect into consideration, is proposed to predict the premixed turbulent burning velocity, using the local burning velocity as a reference instead of the original laminar burning velocity. The model can be explained as follows. The turbulence affects the turbulent burning velocity by increasing the flame surface area and stretching the flame. Consequently, the turbulent burning velocity and quenching limit are determined by the balance of both effects. The predicted velocities are compared with the measured turbulent burning velocities where the fuel, equivalence ratio and the laminar burning velocity were varied extensively. As a result, quantitative accuracy of this simple model is confirmed.
The use of coloured smoke to visualize secondary flows in a turbine-blade cascade

A coloured-smoke-visualization technique has been developed for the investigation of complex three-dimensional fluid flows. In particular, a coloured-smoke wire technique is used for the study of secondary flows in straight turbine cascades. Based on a large number of photographs and direct flow observation, the evolution of horseshoe and passage vortices through a high-turning turbine-blade passage is described.
Predicting Hurricane Intensity and Associated Hazards: A Five-Year Real-Time Forecast Experiment with Assimilation of Airborne Doppler Radar Observations

AbstractPerformance in the prediction of hurricane intensity and associated hazards has been evaluated for a newly developed convection-permitting forecast system that uses ensemble data assimilation techniques to ingest high-resolution airborne radar observations from the inner core. This system performed well for three of the ten costliest Atlantic hurricanes: Ike (2008), Irene (2011), and Sandy (2012). Four to five days before these storms made landfall, the system produced good deterministic and probabilistic forecasts of not only track and intensity, but also of the spatial distributions of surface wind and rainfall. Averaged over all 102 applicable cases that have inner-core airborne Doppler radar observations during 2008–2012, the system reduced the day-2-to-day-4 intensity forecast errors by 25%–28% compared to the corresponding National Hurricane Center’s official forecasts (which have seen little or no decrease in intensity forecast errors over the past two decades). Empowered by sufficient comp.
Redshifts of quasars in the CFHT/MMT survey - Further evidence for isolated groups

The results of MMT spectroscopic observations of 248 quasars discovered in the CFHT grens survey are presented. Many more quasars with z about 1.1 in the 1338+27 field have been found, providing additional evidence for a physical group of quasars in this direction. An analysis of the clustering properties of the quasar sample indicates that, in agreement with other workers, some quasars are clustered on scales r of less than 10/h Mpc. However, in this case this clustering is largely confined to the above mentioned group which occupies a small fraction of the total volume surveyed. A larger unbiased survey is required in order to investigate how general this result is. 12 refs.
Line integral representation of physical optics scattering from a perfectly conducting plate illuminated by a Gaussian beam modeled as a complex point source

An exact line integral representation of the physical optics fields scattered by a perfectly conducting plate illuminated by a vector complex point source is derived. Complex point sources provide, in the paraxial region, an accurate model of Gaussian beams, and can thus be used to efficiently represent the pattern of directive sources. Numerical results are shown to illustrate the exactness of the procedure and the computation time saving is investigated by comparison with surface integration. Moreover, by analyzing the scattering from a plate illuminated by a corrugated circular horn, the feasibility and accuracy of the proposed approach for modeling scattering due to real sources are demonstrated.
Ultrawide range dielectric spectroscopy of BaTiO3-based perovskite dielectrics

Ultrawide range dielectric spectra from the kilohertz to terahertz range of BaTiO3 (BT), Ba(Zr0.25Ti0.75)O3 (BZT), (Ba0.6Sr0.4)TiO3 (BST), and SrTiO3 ceramics were presented by analyzing dielectric permittivity and IR reflectivity data. It was found that the permittivity of the ST was determined only by the ionic polarization while that of the BT was determined by the ionic polarization as well as the dipole polarization due to the domain contribution. The high permittivity of the BZT ceramics was attributed to the dipole polarization of polar nanoregions in the relaxors. The dipole and ionic polarizations overlapped in the BST.
Generalized fourier transforms and global small solutions to kirchhoff equations

It is proved that the inverse of the generalized Fourier transform associated to V an appropriate compactly supported potential, maps into the space of rapidly decreasing functions. This is used for the study of wave equations with non-local nonlinearities of the type being an exterior domain in R3 with V = 0, assuming Dirichlet boundary conditions for u. For a class of smooth data we obtain global existence of small solutions, as well as a partial characterization of the asymptotic behavior as t→∞ . The existence of global large solutions generated by eigenvectors corresponding to negative eigenvalues of is also investigated.
A formula for the charge form factor of closed-shell nuclei and its application to 16O

An expression for the charge form factor of light closed-shell nuclei previously derived in the framework of the non-unitary model operator approach is simplified by considering normalised correlated wavefunctions of the relative motion that are suitably parameterised. The expression is applied to the 16O nucleus and the correlation parameters (which are taken to be state dependent) together with the harmonic oscillator parameter are determined by fitting to experimental values of the charge form factor of 16O. The diffraction minima are well reproduced.
Optimization procedures for simultaneous road rehabilitation and bridge replacement decisions in highway networks

A road-bridge rehabilitation model is formulated as a mixed non-linear programming problem with linear constraints. The purpose of the model is to minimize user travel costs under limited availability of funds. Two constraints are related to budget availability for road rehabilitation and bridge replacement (or rehabilitation). For a given set of replaced bridges, the problem is reduced to a continuous non-linear programming problem that can be further decomposed into a traffic assignment problem (TAP) and a road rehabilitation budget allocation problem (RBAP). The solution to the non-linear problem is found by iteratively solving the TAP and the RBAP. Since the TAP has a non-convex objective function, its solution is only guaranteed to be a local optimum. Several local optima are obtained at each branch of the search tree to estimate a lower confidence limit on the user cost of a global solution.
Notes on quantum Liouville theory and quantum gravity

There are two motivations to study two-dimensional quantum gravity. First, this theory is a toy model for four-dimensional gravity. Second, two-dimensional quantum gravity is the theory on the world-sheet of both “critical” as well as “non-critical” string theories. Some of our conclusions apply to these two more general situations. Since we would like to draw lessons from this simple theory, which are generic and valid in more complicated systems, we should study it in continuum field theory language. In these notes we review the status of the continuum Liouville approach to quantum gravity. Our understanding of the subject is far from complete. We will point out what we think are the most important open problems, and will speculate about their solutions.
Optimization control of modulation-instability gain in photonic crystal fibres with two-zero dispersion wavelengths

We design three kinds of photonic crystal fibres (PCF) with two zero-dispersion wavelengths (ZDWs) using the improved full vector index method (FVIM) and finite-difference frequency domain (FDFD) techniques. Based on these designed fibres, the effect of fibre structure, pump power and wavelength on the modulation instability (MI) gain in the anomalous dispersion region close to the second ZDW of the PCFs is comprehensively analysed in this paper. The analytical results show that an optimal MI gain can be obtained when the optimal pump wavelength (1530 nm) is slightly shorter than the second ZDW (1538 nm) and the optimal pump power is 250 W. Importantly, the total MI gain bandwidth has been increased to 260 nm for the first time, so far as we know, for an optimally-designed fibre with Λ = 1.4 nm and d/Λ = 0.676, and the gain profile became much smoother. The optimal pump wavelength relies on the second ZDW of the PCF whereas the optimal pump power depends on the corporate operation of the optimal fibre structure and optimal pump wavelength, which is important in designing the most appropriate PCF to attain higher broadband and gain amplification.
The Mass Function of Clusters of Galaxies

The mass function of clusters of galaxies is derived separately from optical and X-ray observations of their respective properties. The mass function was extended to the faint end, to lower masses than the rich clusters, using small groups of galaxies. The derived mass function is within the mass range from approximately 10 exp 12 to not less than 10 exp 15/h solar masses. The deduced density range n is approximately 10 exp -2 to 10 exp -8 cubic h/cubic Mpc. The observed shape of the mass function exhibits a shallow power-law decrease with mass at the faint end, and a steep exponential decrease with mass at the massive end. A summary of some constraints placed by the observed mass function on current cosmological models is presented.
Treatments of Missing Data: A Monte Carlo Comparison of RBHDI, Iterative Stochastic Regression Imputation, and Expectation-Maximization

This article describes a Monte Carlo investigation of 4 methods for treating incomplete data. Data sets conforming to a single structured model, but varying in sample size, distributional characteristics, and proportion of data deleted, were randomly produced. Resemblance-based hot-deck imputation, iterated stochastic regression imputation, structured-model expectation-maximization, and saturated-model expectation-maximization were applied to these data sets, and these methods were then compared in terms of their ability to reconstruct the original data, the intact-data variances and covariances, and the population variances and covariances. The results favored the expectation-maximization methods, regardless of sample size, proportion of data missing, and distributional characteristics of the data. The results are discussed with respect to practical considerations in the choice of missing-data treatment, including the possibilities of model misspecification, convergence failure, and the need to make data available to other investigators.
Pressure Distribution in Cavitating Circular Cylinder Wakes

The present study examines the effect of cavitation on the base pressure coefficient of a circular cylinder. The tests are conducted at near-constant Reynolds numbers (≈105) and a wide range of cavitation numbers. The degree of cavitation varies from noncavitating flow, to inception, to near-choking conditions. Pressure measurements along the wake axis are also obtained at various cavitation numbers. The similarity of the wake axis pressure distribution is investigated.