Miracle-dz/UniFAR-FTUs huggingface dataset:
An asymptotic theory for the generation of nonlinear surface gravity waves by turbulent air flow

Based on a previous linear theory (van Duin & Janssen 1992), turbulent air flow over a surface gravity wave of finite amplitude is studied analytically by the methods of matched asymptotic expansions and multiple-scale analysis. In particular, an initial-value problem for weakly nonlinear waves is solved, where the initial conditions are prescribed by a single Stokes wave, displacing the water surface. The water is inviscid and incompressible, and there is no mean shear current. Wave–wave interactions are not taken into account. The validity of the theory is restricted to slow waves and small drag coefficient. We investigate in detail the change of the mean air flow with the evolution of the wave, with a prescribed order of magnitude of the initial wave slope. The rate of change of this flow is fully determined by an evolution equation for the wave slope, which is obtained from the continuity condition for the normal stress at the air-water interface. This equation also determines the amplitude-dependent rate of growth or damping of the wave, for which a closed-form expression is derived. It turns out that nonlinear effects reduce the rate of energy transfer from the mean air flow to the growing wave, which implies that nonlinearity has a stabilizing effect. For sufficienty large time scales, the slope of the growing wave becomes so large that the original evolution equation, which is approximately a Landau equation, ceases to be valid. For such relatively large wave slope, an alternative evolution equation is derived, which presumably describes the further evolution of the wave until the occurrence of wave breaking. The relative effects of nonlinearity, which can be characterized by a single parameter, increase with increasing wave slope and decreasing wave frequency.
Surface plasmon excitation of Au and Ag in scanning probe energy loss spectroscopy

We explore the incident energy dependence of the electronic excitation spectra of Au and Ag films in scanning probe energy loss spectroscopy (SPELS) and also high resolution electron energy loss spectroscopy. We show that the spectra obtained in SPELS depend strongly on the incident electron beam energy. In the case of Au, interband transitions mask the surface plasmon unless the field emission voltage is reduced to ∼100 V, whereas there is a clear surface plasmon peak above 300 V for Ag.
An unusual jetlike feature associated with the Seyfert galaxy Markarian 315

Cette caracteristique est visible sur les images CCD obtenues avec des filtres a bande etroite centres sur les raies [OIII] et Hα decalees vers le rouge, mais pas en lumiere continue. La source de son ionisation doit se trouver dans le noyau. Il se pourrait qu'elle resulte de l'interaction avec une autre galaxie
PERMANENCE AND UNIFORMLY ASYMPTOTICAL STABILITY OF ALMOST PERIODIC SOLUTIONS FOR A SINGLE-SPECIES MODEL WITH FEEDBACK CONTROL ON TIME SCALES

In this paper, using the time scale calculus theory, we first discuss the permanence of a single-species model with feedback control on time scales. Based on the permanence result, by the Lyapunov functional method, we establish sufficient conditions for the existence and uniformly asymptotical stability of almost periodic solutions of the considered model. Moreover, we present an illustrative example to show the effectiveness of obtained results.
An experimental study to select aggregate gradation for stone mastic asphalt

The present study evaluates the effect of aggregate gradation with different nominal maximum aggregate sizes on the stiffness, rutting, and fatigue performance of stone mastic asphalt (SMA). These performance parameters are important in mechanistic-empirical pavement design. Four SMA mixes with 4.75, 9.5, 12, and 19 mm nominal maximum size of aggregate in aggregate gradation and a PG 58-22 asphalt binder were designed. Dynamic modulus, wheel tracker, and four-point beam fatigue tests were conducted at different temperatures. A regression model has been utilized using wheel tracker test data, which reveals that rut resistance of SMA increases with an increase of aggregate size in aggregate gradation. Beam fatigue testing and asphalt binder drain down testing indicate that increasing aggregate size in an aggregate gradation decreases fatigue life and increases binder drainage, respectively. This study also reports some relationships between dynamic modulus, wheel tracker rut depth and fatigue life of SMA. A relationship between fatigue coefficients (K1 and K2) obtained from the fatigue curves has also been proposed. Analysis of results indicates that stiffer SMA has lower fatigue life and rut values. Rut resistance and mix stiffness increase with an increase in aggregate size in an aggregate gradation.
Evolution of Archaea in 3D modeling

The analysis of all groups of Archaea performed in two-dimensions have demonstrated a specific distribution of Archaean species as a function of pH/temperature, temperature/salinity and pH/salinity. Work presented here is an extension of this analysis with a three dimensional (3D) modeling in logarithmic scale. As it was shown in 2D representation, the “Rules of the Diagonal” have been expressed even more clearly in 3D modeling. In this article, we used a 3D Mesh modeling to show the range of distribution of each separate group of Archaea as a function of pH, temperature, and salinity. Visible overlap and links between different groups indicate a direction of evolution in Archaea. The major direction in ancestral life (vector of evolution) has been indicated: from high temperature, acidic, and low-salinity system towards low temperature, alkaline and high salinity systems. Specifics of the geometrical coordinates and distribution of separate groups of Archaea in 3 D scale were analyzed with a mathematical description of the functions. Based on the obtained data, a new model for the origin and evolution of life on Earth is proposed. The geometry of this model is described by a hyperboloid of one sheet. Conclusions of this research are consistent with previous results derived from the two-dimensional diagrams. This approach is suggested as a new method for analyzing any biological group in accordance to its environmental parameters.
On the time to extinction in recurrent epidemics

An approximation is derived for the expected time to extinction in a stochastic model for recurrent epidemics. Numerical illustrations indicate that the approximation is crude but that it has the correct order of magnitude. The quasi‐stationary distribution plays an important role in the derivation. Approximations for the critical community size and of the persistence threshold are derived. Comments are made on the classical study by Bartlell (1956–1960).
Abundances in globular cluster red giants. II. M92 and M15.

A detailed abundance analysis is performed for four stars in M92 and two stars in Ml5 by using LTE line-blanketed model atmospheres. The deduced result of [Fe/H] with respect to the Sun is —2.35 for M92 and —2.20 for Ml5. There are no obvious changes in the pattern of abundance as a function of atomic number except for a general lowering by a constant factor when M92 and M13 are compared. The dispersion in the Fe abundance of the M92 stars is very small. Implications for the mass and number of previous generations of stars and for mixing in the protoglobular cluster are discussed.
Surface processing technique based on opto-hydrodynamic phenomena occurring in laser-induced breakdown of a microdroplet

We report the development of a surface processing technique based on the optical breakdown of a microdroplet and subsequent ejection of a pulsed microjet. The microjet was sufficiently fast to remove nanoparticles from surfaces and erode most materials. The small volume of the droplet enabled precise and selective treatment of surfaces. When the jet was impinged onto a laser spot focused by the droplet, ablation rates substantially larger than those in conventional pulsed laser ablation were obtained with significantly reduced thermal effects. The jet could remove 20 nm particles and an oxide layer from solid surfaces by hydrodynamic impact only.
Young stellar disks formed by the collision of a molecular cloud with a circumnuclear disk at the Galactic center

Abstract We suggest a new formation mechanism for the inclined, sub-parsec scale and counterrotating stellar disks observed around the central black hole in the Milky Way Galactic center. The simulation of a single molecular cloud crashing into a circumnuclear ring of gas leads to the inflow of multiple streams of gas towards the central parsec region. The time delayed arrival of those streams forms multiple, sub-parsec scale accretion disks, with angular momentum depending on the ratio of cloud and circumnuclear ring material. These accretion disks could then be the progenitors which fragmented into the observed stellar disks. A similar event might have also led to the creation of the so-called minispiral in the Galactic center.
Deep Inference and the Calculus of Structures

The calculus of structures is a new proof theoretical formalism, introduced by myself in 1999 andinitially developed by members of my group in Dresden since 2000. It exploits a new symmetrymade possible by deep inference. We can present deductive systems in the calculus of structures andanalyse their properties, as we do in the sequent calculus, natural deduction and proof nets. Typicalproperties of interest are normalisation and cut elimination. There are now many researchersaround the world developing deep inference and investigating its consequences on proof theory.This document gives an overview of this research eﬀort. The main purpose of our new formalism is to allow a richer combinatorial analysis of proofsthan the other formalisms do. We adopted two main ideas: inferences are symmetric betweenpremises and conclusions, and they are deeply applicable inside expressions, what we call deepinference. As a consequence, it is convenient to deduce over structures, which are expressionsintermediate between formulae and sequents.The calculus of structures generalises straightforwardly the sequent calculus, but it allowsmore freedom in the design of deductive systems. We can in fact design systems where all rules areatomic, or local, including contraction, promotion, all the additive rules and, most importantly, thecut rule. In particular, the cut rule gets decomposed into several rules, all independently admissible.The proof theory of the calculus of structures diﬀers signiﬁcantly from what has been studiedso far. Deep inference severely challenges the usual cut elimination methods, but this is mitigatedby atomic cuts being much simpler objects than generic cuts.We developed several new techniques to overcome the diﬃculties. Some of these methodsallowed us to unveil totally new combinatorial properties of logical systems, like the decompositiontheorems. In general, the new properties have a strong ﬂavour of modularity. This, together withatomicity and locality, is important for applications in computer science, which we recently startedto pursue.We presented in the calculus of structures classical logic, intuitionistic logic, modal logic,linear logic and several non-commutative linear logics, in such a way that atomicity, locality andthe various instances of modularity can been expressed. The deductive systems in the calculus ofstructures are simple and elegant, and they pose no special challenge to those interested in usingthem. Moreover, the calculus of structures is inspiring a new generation of proof nets with better
Characterization of Plasma Flow through Magnetic Nozzles

Abstract : This report is an account of research undertaken to describe the steady, axisymmetric flow of plasmas through rocket nozzles, with attention directed to the use of magnetic fields for guiding or propelling the plasmas. The primary emphasis is on simply connected nozzles containing strictly longitudinal (B sub r, O, B sub z) magnetic fields to guide the plasma, with secondary consideration given to annular nozzles containing strictly azimuthal (O, B sub theta, O) magnetic fields to propel the plasma. The possibility and desirability of using hot plasmas in a repetitive mode is discussed, and motivates our consideration of an extensive range of parameters. Although slightly ionized gases having low temperatures (a fracture of an eV) and low magnetic Reynolds numbers often are the objects of valid and useful research (for example, in connection with MHD generators, with MPD thrusters, and with arc heaters to provide sources of hot gas for expanding gas-dynamic flow fields) , the focus is upon the effective and efficient interaction of substantial plasmas with guiding or driving magnetic fields. Thus, focus is primarily on highly ionized plasmas that are not dominated by resistive dissipation. Some of the principal physics issues associated with these concepts are addressed, including the assumptions and limitations of the ideal MHD model, the magnitude and scaling of classical and anomalous transport losses and of radiation losses in hydrogen plasma during transit of plasma through the nozzle, and the transport-related detachment problem of how the plasma leaves the exit region of the nozzle.
Variability of GRF Components between Increased Running Times during Prolonged Run

A study was conducted to investigate the possible effects of fatigue which was resulted from increased running time on the sta- bility during a prolonged run. The purposes of this study were twofold: first, to determine the discrete and non-linear variability of GRF (ground reaction force) components between running times to know the body stability, and second, to determine the pat- tern between discrete and non-linear variability. Nineteens healthy young adult males served in this study as subjects who ran at their preferred running speed. GRF data for twenty strides were collected at 5, 65, and 125 minutes during run. Variance coefficient and Lyapunov Exponent techniques on the GRF data were used to calculate variability index for each of the running time con- ditions. There were no difference between discrete variabilities of three components of GRF, but non-linear variability of the Fz component of GRF was decreased by increasing running time (p<.01). No relationship was found between discrete and non-linear variability
Spectral irradiance calibration in the infrared. II - Alpha Tau and the recalibration of the IRAS low resolution spectrometer

A general process for creating complete, continuous, and absolutely calibrated 1-35 micron stellar spectra is described. The method is demonstrated by constructing an absolutely calibrated 1-35 micron spectrum of Alpha Tau and the method is independently validated using new observations. The absolute calibration of the IRAS low resolution spectrometer (LRS) data base is investigated by comparing the observed spectrum of Alpha Tau with that assumed in the original LRS calibration scheme. An analysis of asteroidal LRS spectra results in an independent assessment of the calibration problems with the LRS and provides a natural complement to the effort based on Alpha Tau. A direct comparison of LRS stellar spectra with independently calibrated long-wavelength airborne and ground-based spectra is made.
X-ray magnetic circular dichroism study of the decoupling of the magnetic ordering of the Er and Co sublattices in Er1-xYxCo2 systems

We present an x-ray magnetic circular dichroism (XMCD) study performed at the Co $K$ edge and at the Er ${L}_{2,3}$ edges in the ${\mathrm{Er}}_{1\ensuremath{-}x}{\mathrm{Y}}_{x}{\mathrm{Co}}_{2}$ series. Our results indicate that both Er and Co magnetic sublattices order at the same temperature for all the investigated compounds. In the case of the ${\mathrm{Er}}_{0.6}{\mathrm{Y}}_{0.4}{\mathrm{Co}}_{2}$ compounds, XMCD data do not show the decoupling of the magnetic ordering for both Er and Co sublattices. Moreover, no experimental evidence of the occurrence of an inverse itinerant electron metamagnetism has been found for applied magnetic fields of up to ${\ensuremath{\mu}}_{0}H=10\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. In addition, a nonzero magnetic moment is found at the Co sites in the case of the ${\mathrm{Er}}_{0.5}{\mathrm{Y}}_{0.5}{\mathrm{Co}}_{2}$ compound.
Existence and uniqueness for electrode models for electric current computed tomography

The following experiment is considered. To a body of given conductivity, a number of electrodes are attached, through which current is sent. On the same electrodes, the resulting voltages are measured. This experiment can be described by a number of mathematical models [K. -S. Cheng et al., IEEE Transactions on Biomedical Engineering, 36 (1989), pp. 918–924]. These models are discussed and their predictions compared with experiment. In particular, a model is exhibited that is capable of predicting the experimentally measured voltages to within 0.1 percent. For this model, existence and uniqueness of the associated electrical potential is proved.
Detection of clump and interclump gas in the Rosette Molecular Cloud Complex

Resultats d'observations CO et 13 CO de haute resolution et haute sensibilite du complexe Rosette. Les grumeaux sont facilement identifiables, leur densite etant ∼10 fois superieure a la densite moyenne du complexe. Le gaz n'est pas lie gravitationnellement au complexe
The analysis of the dynamic behavior of the electro-optical bistable systems

In this paper, research on the dynamic behaviors of the electro-optical bistable system, especially for its chaotic dynamic behavior, was carried out. The dynamic equation is resolved by the method of the diagrammatized mode. The state of the electro-optical bistable system with changing system parameter is analyzed in detail, and the concrete positions of the bifurcation points are calculated. The system can generate tangent bifurcation and period double bifurcation as the systemic parameter changes, thus the system can generate chaos through period double bifurcation; on the other hand, the system can generate intermittent chaos.
Positive Cloud-to-Ground Lightning in Mesoscale Convective Systems

Abstract We have examined the characteristics of positive cloud-to-ground lightning flashes in Mesoscale Convective Systems observed during the Oklahoma-Kansas PRE-STORM project in 1985. Lightning frequencies and patterns of ground strike locations are related to observed storm precipitation structures, with emphasis placed on relating observed lightning patterns to the stratiform precipitation regions. Positive ground flashes are categorized in relation to their position relative to storm radar echo patterns, and frequency of occurrence relative to storm lifecycles. Observations presented indicate that many of the positive flashes are likely produced by the advection of positive charge from the upper levels of the convective portions of the storm. We suggest that an additional class of positive ground flashes are associated with the generation of charge by stratiform precipitation processes, specifically related to ice-ice interactions in regions of low supercooled liquid water contents. A simple one-dim.
Interaction of Upper-Tropospheric Turbulence and Gravity Waves as Obtained from Spectral and Structure Function Analyses

Abstract Spectral and structure function analyses of horizontal velocity fields observed in the upper troposphere and lower stratosphere during the Severe Clear Air Turbulence Collides with Air Traffic (SCATCAT) field program, conducted over the Pacific, were carried out in an effort to identify the scale interactions of turbulence and small-scale gravity waves. Because of the intermittent nature of turbulence, these analyses were conducted by clearly separating out the cases when turbulence did or did not occur in the data. In the presence of turbulence, transitional power spectra from k−2 to k−5/3 were found to be associated with gravity waves and turbulence, respectively. The second-order structure function analysis was able to translate these spectral slopes into r and r 2/3 scaling, consistent with the Monin and Yaglom conversion law, in physical space, which presented clearer pictures of scale interactions between turbulence and gravity waves. The third-order structure function analysis indicated th.
Skyrme model description of heavy baryons with strangeness

Skyrme Model Description of Heavy Baryons with Strangeness J.P. Blanckenberg Department of Physics, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa. Dissertation: PhD Theoretical Physics March 2015 We are interested in the soliton description of baryons with a single heavy quark (charm or bottom). In this approach such baryons emerge as bound composites of a soliton of meson elds built from light quarks (up, down and strange) and a meson eld that contains a heavy quark. The soliton must then be quantised as a diquark because the fermionic character arises from binding the heavy meson eld. We are particularly interested in heavy baryons that have non-zero strangeness. In the quark model that corresponds to, say, up-strange-bottom (usb) baryons. Thus the avour symmetry breaking among the light quarks must be fully incorporated when constructing diquark states. In the soliton model that symmetry breaking is parameterised by di erences between the masses and decay constants of kaons and pions. Here we will compute the mass di erences between the di erent heavy baryons and compare these results to experimental data. ii Stellenbosch University https://scholar.sun.ac.za
Twin convergence regions for continued fractions

(1.5) | a2n+i| ^ * 2 < 1, U2«| £ (1 + ky + e (e> 0), the continued fraction (1.1) converges. For k<l this result can be shown to be a "best" result except possibly for the presence of the quantity e. The present paper is concerned with establishing convergence criteria of this general type. The principal result is given in Theorem 3.1. The method to be used is the following. Denote the nth. approximant of (1.1) by An/Bn. Conditions on the numbers an are determined which imply that the approximants lie in a given region V of the complex plane. A continued fraction the elements of which are functions of the complex variable z and which reduces to (1.1) for 2 = 1 is then introduced. When the given conditions on the numbers an are satisfied the approximants of this continued fraction are shown to
On the twistor description of massive fields

This paper forms a part of the twistor programme whereby constructions of physics on Minkowski space are transferred, it is hoped, to simpler constructions on Penrose’s twistor-space. We show how the Penrose transform may be used to describe solutions of the Dirac equations on Minkowski space in terms of certain cohomology classes on a related five-dimensional complex manifold. This is accomplished along the same lines as the corresponding representation of massless fields. It means that Penrose’s integral formulae for massive fields may be interpreted cohomologically. We also give a brief discussion of the spin operator in twistor space.
Comparison of Voyager Shocks in Solar Cycle 23

Solar cycle 23 was notable for two periods of intense solar activity (or ‘events’ as we shall hereafter refer to them): the ‘Bastille Day Event’ of 2000 and the ‘Halloween Event’ of 2003. In this paper we look at the signatures of the interplanetary shocks produced by these events, in particular the plasma parameters, as observed by Voyager 2 (V2) some six months after the events occurred at Sun. We compare these shocks with other large events observed by V2 during the preceding decade. We note that the plasma parameters, most notably the plasma density, are frequently not as might be expected for “typical” events.