Miracle-dz/UniFAR-FTUs huggingface dataset:
Large-Eddy Simulations of Fully Developed Turbulent Channel and Pipe Flows with Smooth and Rough Walls

Studies in turbulence often focus on two flow conditions, both of which occur frequently in real-world flows and are sought-after for their value in advancing turbulence theory. These are the high Reynolds number regime and the effect of wall surface roughness. In this dissertation, a Large-Eddy Simulation (LES) recreates both conditions over a wide range of Reynolds numbers Reτ = O(102)-O(108) and accounts for roughness by locally modeling the statistical effects of near-wall anisotropic fine scales in a thin layer immediately above the rough surface. A subgrid, roughness-corrected wall model is introduced to dynamically transmit this modeled information from the wall to the outer LES, which uses a stretched-vortex subgrid-scale model operating in the bulk of the flow. Of primary interest is the Reynolds number and roughness dependence of these flows in terms of first and second order statistics. The LES is first applied to a fully turbulent uniformly-smooth/rough channel flow to capture the flow dynamics over smooth, transitionally rough and fully rough regimes. Results include a Moody-like diagram for the wall averaged friction factor, believed to be the first of its kind obtained from LES. Confirmation is found for experimentally observed logarithmic behavior in the normalized stream-wise turbulent intensities. Tight logarithmic collapse, scaled on the wall friction velocity, is found for smooth-wall flows when Reτ ≥ O(106) and in fully rough cases. Since the wall model operates locally and dynamically, the framework is used to investigate non-uniform roughness distribution cases in a channel, where the flow adjustments to sudden surface changes are investigated. Recovery of mean quantities and turbulent statistics after transitions are discussed qualitatively and quantitatively at various roughness and Reynolds number levels. The internal boundary layer, which is defined as the border between the flow affected by the new surface condition and the unaffected part, is computed, and a collapse of the profiles on a length scale containing the logarithm of friction Reynolds number is presented. Finally, we turn to the possibility of expanding the present framework to accommodate more general geometries. As a first step, the whole LES framework is modified for use in the curvilinear geometry of a fully-developed turbulent pipe flow, with implementation carried out in a spectral element solver capable of handling complex wall profiles. The friction factors have shown favorable agreement with the superpipe data, and the LES estimates of the Karman constant and additive constant of the log-law closely match values obtained from experiment.
Self-irradiated cooling condensations - The source of the optical line emission from cooling flows

The optical filaments seen at the centers of clusters of galaxies, which cannot be explained by standard photoionization or shock models, can be straightforwardly interpreted as self-irradiated cooling condensations. Fully developed (about 10,000 K) condensations embedded in thermally unstable 10 million K gas will be bathed in a powerful EUV/soft X-ray flux emanating from the surrounding condensing regions. The present models of the condensation/irradiation process give line ratios and luminosities similar to those observed. Because it is assumed that the condensations arise from linear perturbations, which grow significantly only when the local cooling time is less than the free-fall time, condensing regions of the type modeled here should arise only in cooling flows of central pressure less than about 1 billion ergs/cu cm and should extend only over the inner regions of the cluster. 24 refs.
Transmission electron microscopy study on ferromagnetic (Ga,Mn)N epitaxial films

We report on the crystal structure of epitaxial (Ga,Mn)N films with Mn=0.2% grown by plasma-enhanced molecular beam epitaxy, exhibiting n-type conductivity and room temperature ferromagnetism (Ms=0.76 emu/cm3, Hc=90 Oe). The additional diffraction spots are found in the zone axis of B=[1100] for the (Ga,Mn)N epilayer due to a single twin orientation in the closed packed hexagonal matrix. High-order Laue zone measurements reveal the expansion of lattice parameter a (3.1851–3.1865 A) by doping Mn, demonstrating that Mn ions substitute for Ga ions in the (Ga,Mn)N.
Martensitic transformation and magnetic field-induced strain in Fe–Mn–Ga shape memory alloy

Martensitic and magnetic properties of Fe–Mn–Ga single and polycrystalline alloys were investigated. It was found that Fe–Mn–Ga alloys exhibit martensitic transformation from the paramagnetic L21 Heusler parent phase to the ferromagnetic L10 martensite phase. The martensitic transformation temperatures increased by about 20 K by the application of a magnetic field of 7 T, and a metamagnetic phase transition was observed. In addition, a magnetic field-induced strain of 0.6% associated with magnetic field-induced forward transformation was confirmed in an Fe43Mn28Ga29 single crystal.
Regularization approach to multisensor reconstruction

Due to the presence of noise and uncertainty, a single set of visual data is not always sufficient to successfully perform the intended vision task. In this paper, we consider the visual reconstruction problem with multi-sensor data and propose a computational method for fusion of sensor information. Correlation among different sensor information appears in some hidden representation of data. In our representation of visual data, the fusion of information occurs at the places where visual discontinuities appear. The appearance of discontinuities in one set of data is constrained by the discontinuity contours in other sets of data. This is achieved by introducing energies of external discontinuity cliques of multiple sensor data to the minimizing energy functional. The fusion improves the reconstruction error in individual sensors, and the detection of discontinuities, and reduces the false detection of discontinuities. The computational method presented in this paper can deal with fusion of surfaces with higher order discontinuities and with data sets belonging to different visual cues. Previously proposed Markov Random Field (MRF) techniques can deal with surfaces having only first order discontinuities. An implementation of the proposed fusion method on simulated images, and a comparison of the results with the other methods are presented.
Correlation of spectral luminescence with threading dislocations in green-light-emitting InGaN quantum wells

A direct correlation has been established between the spatial variation of spectral luminescence and the distribution of threading dislocations in a green-light-emitting InGaN quantum well structure grown on a sapphire substrate. Transmission electron microscopy and monochromatic cathodoluminescence images, taken from the same region, indicate that the nature of the quantum well emission is influenced by the microstructure of the underlying GaN. The microstructure is defined by threading dislocations that reflect a columnar structure with low-angle grain boundaries. A strong correlation is observed between this microstructure and the peak and low-energy portion of the quantum well luminescence, with threading dislocations as boundaries between bright and darker regions. The high-energy portion of the luminescence is localized and is generally complementary to the rest of the spectrum.
Bremsstrahlung and energetic electrons in supernovae

Explicit Monte Carlo calculations are presented for the rate of Compton scattering and for the spectrum recoil electrons per gram at discrete depths within models of supernovae, with emphasis on the bremsstrahlung emissivity within supernova interiors. The spectrum of the bremsstrahlung emissivity is calculated at E to the -1.3 for a wide range of supernova models. The radial and temporal dependence of that emissivity is calculated for two models of SN 1987A and for one model of a Type Ia and of a He core explosion model of a Type Ib. The spectrum emerging from the surface, which is then evaluated by Monte Carlo techniques, was found to be sensitive to the photoelectric opacity and inverted by it, i.e., the spectral luminosity of the bremsstrahlung component increases slowly between 1 and 30 keV even though the emissivity declines with energy within that energy band. The bremsstrahlung luminosity was found to dominate that of the primary scattered gammas for E of less than 20 keV. 34 refs.
H I studies of the Sculptor group galaxies. VII: Implications on the distribution and nature of dark matter in groups

Results from the large-scale mapping of the H I gas in the Sculptor group are presented. From the kinematical analysis of the members, a mean value of (M/L B ) global = 9 ± 5 M ⊙ /L ⊙ (at the last observed velocity point) is found for the individual galaxies. This is a factor ∼10 smaller than the (M/L B ) dyn = 90 ± 20 M ⊙ /L ⊙ derived from a dynamical study of the whole group. Mass models, fitted to the rotation curves, suggest a mean density of dark matter (DM) of ∼5×10 −3 M ⊙ pc −3 in the halos of the galaxies.
The Kalman-Bucy filter accuracy in the guaranteed estimation problem

The optimal guaranteed a priori estimation problem is considered. The Kalman-Bucy filter is used for the approximate solution of this problem. An analytical estimate for the nonoptimality degree of the Kalman-Bucy filter is obtained. This estimate is determined solely by the Kalman-Bucy filter characteristics. Thus the Kalman-Bucy filter efficiency can be established without accurate solution of the difficult optimal guaranteed estimation problem. <<ETX>>
3D-image restoration technique using Genetic Algorithm to solve blurring problems of images

Abstract Most images may not be sharp and clear due to various reasons like noise interference and is said to be in a blurred condition. Image de-blurring is fundamental in making pictures sharp and useful. Normally, along with the input blurred image, Point Spread Function (PSF) of the original image is required for the process of restoration and de-blurring. In this paper, we introduce a technique for image restoration by Richardson–Lucy algorithm where the optimised PSF is generated by the use of Genetic Algorithm (GA). Use of optimised PSF ensures that our proposed technique does not need the original image for the de-blurring purpose and can be greatly beneficial in the real time scenario cases. The dataset used for the evaluation of the proposed technique are real 3D images and the evaluation metrics used are peak signal-to-noise ratio (PSNR), Second-Derivative like Measure of Enhancement (SDME) and mean squared error (MSE). The technique is compared with existing techniques such as de-convolution method, regularisation filter, Wiener filter and Richardson–Lucy algorithm. From the results, we can observe that our proposed technique has achieved higher PSNR and SDME values and lower MSE values when compared with other techniques. We have achieved average PSNR of 70·94, SDME of 71·46 and MSE of 0·0063. The values obtained show the superior performance of the proposed technique.
Positive Solutions of Yamabe Type Equations on Complete Manifolds and Applications

We study the semilinear equationΔu+a(x) u=b(x) uσ(σ>1) on a complete Riemannian manifold. We determine conditions on the coefficients that guarantee existence and nonexistence of positive solutions. A very general uniqueness result is also established. Our main results are valid without explicit curvature assumptions, and appear to be new even in Rm.
Wrinkled and slack membranes: nonlinear 3D elasticity solutions via smooth DMS‐FEM and experiment

The smooth DMS‐FEM, recently proposed by the authors, is extended and applied to the geometrically nonlinear and ill‐posed problem of a deformed and wrinkled/slack membrane. A key feature of this work is that three‐dimensional nonlinear elasticity equations corresponding to linear momentum balance, without any dimensional reduction and the associated approximations, directly serve as the membrane governing equations. Domain discretization is performed with triangular prism elements and the higher order (C1 or more) interelement continuity of the shape functions ensures that the errors arising from possible jumps in the first derivatives of the conventional C0 shape functions do not propagate because the ill‐conditioned tangent stiffness matrices are iteratively inverted. The present scheme employs no regularization and exhibits little sensitivity to h‐refinement. Although the numerically computed deformed membrane profiles do show some sensitivity to initial imperfections (nonplanarity) in the membrane profile needed to initiate transverse deformations, the overall patterns of the wrinkles and the deformed shapes appear to be less so. Finally, the deformed profiles, computed through the DMS FEM‐based weak formulation, are compared with those obtained through an experiment on an ultrathin Kapton membrane, wherein wrinkles form because of the applied boundary displacement conditions. Comparisons with a reported experiment on a rectangular membrane are also provided. These exercises lend credence to the feasibility of the DMS FEM‐based numerical route to computing post‐wrinkled membrane shapes. Copyright © 2012 John Wiley & Sons, Ltd.
Cochlear reflectivity and teoae transfer function

Cochlear reflectivity has been theoretically estimated for different otoacoustic emission generation mechanisms, using a standard perturbative approach based on the WKB approximation and the osculating parameters technique. The predictions of theoretical models have been compared with experimental measurements of the TEOAE transfer function at different stimulus levels, between 60 and 90 dB pSPL. The phase-gradient delay of the TEOAE response has also been compared to the estimates of the cochlear transmission delay obtained with time-frequency analysis of the same TEOAE waveforms. Place-fixed and wave-fixed OAE generation mechanisms are discussed in the light of the results.
Nonlinear optical properties of aromatic amino acids in the femtosecond regime

We report experimental and theoretical investigations of the third-order optical nonlinearities of aromatic amino acids (Phenylalanine, Histidine, Tryptophan, and Tyrosine) in aqueous solutions. The Z-scan technique with femtosecond laser pulses at 800 nm was explored for the determination of the nonlinear refractive index, nonlinear absorption coefficient, and the second-order hyperpolarizability of each amino acid. Experimental results were compared with theoretical analysis based on post-Hartree Fock MP2/6-311+G**.
A local probability exponential inequality for the large deviation of an empirical process indexed by an unbounded class of functions and its application

A local probability exponential inequality for the tail of large deviation of an empirical process over an unbounded class of functions is proposed and studied. A new method of truncating the original probability space and a new symmetrization method are given. Using these methods, the local probability exponential inequalities for the tails of large deviations of empirical processes with non-i.i. d. independent samples over unbounded class of functions are established. Some applications of the inequalities are discussed. As an additional result of this paper, under the conditions of Kolmogorov theorem, the strong convergence results of Kolmogorov on sums of non-i.i. d. independent random variables are extended to the cases of empirical processes indexed by unbounded classes of functions, the local probability exponential inequalities and the laws of the logarithm for the empirical processes are obtained.
Natural patterns and wavelets

An introductory review of pattern formation in extended dissipative systems is presented. Examples from many areas of physics are introduced, and the mathematical analysis of the patterns formed by these systems is outlined, for patterns near and far from onset. The wavelet transform is introduced as a useful tool for the extraction of order parameters from patterns.
Hyperfine structure measurements in yttrium I using laser saturation spectroscopy in a sputtered vapour

Magnetic hyperfine interaction constants (A factors) have been determined for six excited levels, 4d5s5p z 2Do1/2, 3/2, 5/2, 7/2,and z 4Do1/2,3/2,5/2,7/2, and the two ground-term levels 4d5s2 a 2D32,5/2/ in yttrium I, using an improved method of saturated absorption spectroscopy in a sputtered vapour. The results for z 4Do12/ and z 4Do7/2 are new, while those for the other excited levels confirm recently reported A factors obtained by level-crossing optogalvanic spectroscopy and by absorption line narrowing. The measured A factors for the excited levels are compared with results of LS-coupling calculations for spd configurations.
Afterpulsing in Geiger-mode avalanche photodiodes for 1.06μm wavelength

We consider the phenomenon of afterpulsing in avalanche photodiodes (APDs) operating in gated and free-running Geiger mode. An operational model of afterpulsing and other noise characteristics of APDs predicts the noise behavior observed in the free-running mode. We also use gated-mode data to investigate possible sources of afterpulsing in these devices. For 30-μm-diam, 1.06-μm-wavelength InGaAsP∕InP APDs operated at 290K and 4V overbias, we obtained a dominant trap lifetime of τd=0. 32μs, a trap energy of 0.11eV, and a baseline dark count rate 245kHz.
Topological origin of quasi-flat edge band in phosphorene

Phosphorene, a honeycomb structure of black phosphorus, was isolated recently. The band structure is highly anisotropic, where the kx direction is Dirac-like and the ky direction is Schrödinger-like. A prominent feature is the presence of a quasi-flat edge band entirely detached from the bulk band in phosphorene nanoribbons. We explore the mechanism of the emergence of the quasi-flat band by employing the topological argument invented to explain successfully the flat band familiar in graphene. The quasi-flat band can be controlled by applying in-plane electric field perpendicular to the ribbon direction. The conductance is switched off above a critical electric field, which acts as a field-effect transistor.
A circular waveguide method for measuring the electromagnetic parameters of chiral materials at microwave frequencies

This paper presents a circular waveguide method for simultaneously measuring the electromagnetic parameters of chiral materials at microwave frequencies. Only the dominant mode of the electromagnetic wave in the circular waveguide is considered. The rotation angle, the axial ratio and the complex reflection coefficients of short-circuited (the sample is backed with metal) and open-circuited (the sample is not backed with metal) samples are measured in the frequency range 8.5-11.5 GHz by using an ordinary microwave circular waveguide measurement system. The complex permittivity, complex permeability and complex chirality parameter are calculated from the measured rotation angle, axial ratio and complex reflection coefficients of short-circuited and open-circuited samples. The dependences of the electromagnetic parameters on the concentrations and handedness of the chiral inclusions are studied. The results agree basically with those obtained by the free-space method.
Singular linear quadratic optimal control for singular stochastic discrete‐time systems

The finite time horizon singular linear quadratic (LQ) optimal control problem is investigated for singular stochastic discrete‐time systems. The problem is transformed into positive LQ one for standard stochastic systems via two equivalent transformations. It is proved that the singular LQ optimal control problem is solvable under two reasonable rank conditions. Via dynamic programming principle, the desired optimal controller is presented in terms of matrix iterative form. One simulation is provided to show the effectiveness of the proposed approaches. Copyright © 2012 John Wiley & Sons, Ltd.
The impact of aerosols on non‐precipitating marine stratocumulus. I: Model description and prediction of the indirect effect

In this paper, the first of a two‐part study, we use the UK Met Office large‐eddy simulation model (LEM) with fully integrated size‐bin‐resolved cloud microphysics (BR‐LEM) to investigate the effects of increasing cloud condensation nuclei (CCN) concentrations on non‐precipitating marine stratocumulus. It is shown, as expected, that increasing CCN concentrations produces an increase in cloud‐drop number concentration and a decrease in cloud‐drop effective radius. However, for the case presented, we demonstrate that increasing CCN concentrations causes an increase in the rate of evaporative cooling at the cloud top, which drives stronger boundary‐layer dynamics, leading to more cloud‐top entrainment, which results in a reduction in boundary‐layer relative humidity and a reduction in LWP with increasing CCN. Comparison of the BR‐LEM simulations with LEM simulations that employ a simpler single‐moment bulk scheme (Bulk‐LEM) show that the bulk microphysics scheme fails to simulate this CCN‐‐entrainment feedback and the associated reduction in liquid water path. It is shown that, for a very polluted case, the failure of the bulk microphysics to capture this evaporation‐‐entrainment feedback results in a 60% overestimation of the indirect forcing estimate compared to the BR‐LEM. We conclude that it is necessary to realistically simulate the dynamic feedbacks associated with increased CCN, otherwise the indirect will be overestimated. Copyright © 2008 Royal Meteorological Society
Ginzburg-Landau theory of superfluidity near absolute zero

Due to strong interactions between superfluid particles, many particles are not in the condensate near absolute zero. In nonequilibrium situations produced under external stirring, they contribute to the flow via their induced average macroscopic motion. We present a modification of the Bose condensate model that considers this induced internal motion. Specifically, we show that the velocity field of the internal motion acts as a gauge field with which the condensate interacts, thereby coupling the applied vorticity to the superflow. The resulting Ginzburg-Landau-like model predicts the flow phenomena observed near absolute zero, in particular, transition to turbulence.
A new perturbative approach to nonlinear problems

A recently proposed perturbative technique for quantum field theory consists of replacing nonlinear terms in the Lagrangian such as φ4 by (φ2)1+δ and then treating δ as a small parameter. It is shown here that the same approach gives excellent results when applied to difficult nonlinear differential equations such as the Lane–Emden, Thomas–Fermi, Blasius, and Duffing equations.
Wide area persistent surveillance with no gimbal

Modern aerial video has depended on high quality gimbals. The benefits of these gimbals include motion correction, navigational information, and a standardized mounting interface for sensors to the platform. The downside to the gimbal is the weight, power, and cost of the system, as well as the potential for mechanical failure. These negative factors are increasingly significant as medium sized and small unmanned aircraft proliferate. Luckily, in many cases, it is possible to fly without a gimbal. With the advent of large format video systems, we can achieve high quality video in the visible domain with un-gimbaled video. The massive field of view and high resolution given by these new systems provides a large amount of data redundancy, and it is possible to use this redundancy to improve algorithmic stabilization, to overcome aircraft motion, and to sharpen geolocation estimates. We describe an example system that flies without a gimbal and detail the algorithms that facilitate the high quality of the video. We present actual imagery from a system with no gimbal with relevant data to evaluate its performance, and we discuss the tradeoffs involved in system design with and without a gimbal.