Miracle-dz/UniFAR-FTUs huggingface dataset:
Unstable periodic orbits and semiclassical quantisation

The Bohr-Sommerfeld quantisation condition has a meaningful extension to classically chaotic systems whose periodic (unstable) orbits are isolated. It provides a semiclassical Euler factorisation for the functional determinant of the quantal Hamiltonian, in contrast to the Hadamard infinite product over the eigenvalues by which the exact determinant is defined.
Plasma size and collisionality scaling of ion-temperature-gradient-driven turbulence

Fixed-flux (FF), fixed-gradient (FG) and local fluxtube (FT) gyrokinetic simulations are systematically compared for ion-temperature-gradient (ITG)-driven turbulence. The collisionality (ν*) dependence of ion heat diffusivity is verified through the inter-model comparisons. When the temperature gradient is far from the nonlinear critical value, the FF and FT models give a weak ν*-dependence, while the FG model shows a strong ν*-dependence. The entropy transfer analysis on the zonal-flow saturation mechanisms in the quasi-steady state of the FT simulation provides clear insights on the different ν*-dependence of the turbulent transport and zonal-flow shearing rate in the far-above- and near-critical cases. It has also been revealed that the FG model provides the strong ν*-dependence through the change of ITG-mode stability due to ν*-dependent heating/sink by the adaptive heat source, where the velocity distribution function is deformed. The plasma size (ρ*) scan in the FF simulations show a Bohm-like transport scaling even in a local limit regime, ρ*−1 ⩾ 300, where profile-shear effects are weak. It has been clarified that the transient variations of local power balance are essential mechanisms leading to the Bohm-like heat transport even at similar mean temperature gradients, where the burst amplitude and its frequency increase with the plasma size and the heating power. The mechanism is unique to the FF model. Comparisons of statistical characteristics in the local limit regime show differences in frequency spectra and probability density functions of the heat flux, while zonal-flow structures and avalanche propagations properties are similar among these models.
Parallel 3‐D simulation of seismic wave propagation in heterogeneous anisotropic media: a grid method approach

SUMMARY This paper presents a parallel numerical technique for modelling wave propagation in 3-D heterogeneous anisotropic media. The scheme is developed by following a so-called 3-D grid method of the elastic-isotropic case. The proposed parallel algorithm needs small data exchanges between subdomains in contrast to that developed based on other numerical techniques; therefore, it is more suitable for a PC-Cluster. The algorithm is implemented on a mesh of mixed tetrahedrons and parallelepipedons, thus providing an accurate description of arbitrary 3-D surface and interface topographies and an easy generation of a non-uniform, unstructured mesh. The unstructured mesh means that the proposed algorithm can reduce the memory requirement by flexibly assigning small grid spacing in regions with low velocities and larger grid spacing in regions with higher velocities. Like the 3-D grid method, the resulting anisotropic scheme naturally satisfies the free-surface boundary conditions of arbitrary surface topography. As a result, the near-surface scattering effects can be more accurately modelled. The proposed scheme can handle a general anisotropy without any interpolations. In this paper, the transversely isotropic medium with a tilted symmetry axis, as typically caused by a system of parallel cracks or fine layers, is discussed in detail. A paraxial absorbing boundary condition in a 3-D general anisotropic case is also proposed. Comparisons with analytical solutions demonstrate the accuracy of the parallel algorithm. Computed 3-D radiation patterns illustrate shear-wave splitting, as predicted by the theory. We show the generality and flexibility of the algorithm by modelling wave propagation in an anisotropic half-space with a hemispherical crater on the surface and in mixed isotropic/anisotropic models with horizontal and inclined interfaces.
Intercalibrating Microwave Satellite Observations for Monitoring Long-Term Variations in Upper- and Midtropospheric Water Vapor*

AbstractThis paper analyzes the growing archive of 183-GHz water vapor absorption band measurements from the Advanced Microwave Sounding Unit B (AMSU-B) and Microwave Humidity Sounder (MHS) on board polar-orbiting satellites and document adjustments necessary to use the data for long-term climate monitoring. The water vapor channels located at 183.31 ± 1 GHz and 183.31 ± 3 GHz are sensitive to upper- and midtropospheric relative humidity and less prone to the clear-sky sampling bias than infrared measurements, making them a valuable but underutilized source of information on free-tropospheric water vapor. A method for the limb correction of the satellite viewing angle based upon a simplified model of radiative transfer is introduced to remove the scan angle dependence of the radiances. Biases due to the difference in local observation time between satellites and spurious trends associated with satellite orbital drift are then diagnosed and adjusted for using synthetic radiative simulations based on the In.
Asymptotically Linear Elliptic Systems

Abstract In this paper, we prove, under natural assumptions, that the semilinear elliptic system possesses at least one positive solution pair (u, v) ∊ H 1 (R N ) × H 1 (R N ), where f(x, t) and g(x, t) are continuous functions on R N × R and asymptotically linear as t → +∞.
A dynamical model for turbulence. I. General formalism

We propose new dynamical equations to describe fully developed turbulence. We begin with the Wyld equations (WE), which are exact solutions of the NSE. The WE, and their Langevin‐like representation, show that nonlinearities induce a turbulent force ft(k) and a turbulent viscosity νt(k), which are given by an infinite series of Wyld diagrams. The series for νt(k) is renormalizable, and its sum can be found using RNG methods. The result, Eq. (2a), holds for stirring forces fext with an arbitrary correlation function φ and generalizes previous RNG results, which neglected ft and were limited to power law φ∼k1−2e. To recover Kolmogorov law, these earlier RNG‐based theories were forced to introduce an ad hoc stirring force with a prescribed φ∼k−3. By contrast, we show that ∼k−3 belongs to φ, which is the correlation function of ft, and that in the inertial range ft≫fext. The series for φ cannot be summed because of a nonrenormalizable infrared divergence (IR) with an infinite number of divergent irreducible.
Interdependence of absorber composition and recombination mechanism in Cu(In,Ga)(Se,S)2 heterojunction solar cells

Temperature-dependent current-voltage measurements are used to determine the dominant recombination path in thin-film heterojunction solar cells based on a variety of Cu(In,Ga)(Se,S)2 alloys. The activation energy of recombination follows the band gap energy of the respective Cu(In,Ga)(Se,S)2 alloy as long as the films are grown with a Cu-poor final composition. Thus, electronic loss in these devices is dominated by bulk recombination. In contrast, all devices based on absorber alloys with a Cu-rich composition prior to heterojunction formation are dominated by recombination at the heterointerface, with activation energies smaller than the band gap energy of the absorber material. These activation energies are independent from the S/Se ratio but increase with increasing Ga/In ratio.
Physical interpretation of eddy current losses in ferromagnetic materials. I. Theoretical considerations

The basic physical mechanism responsible for the general behavior of eddy current losses versus magnetizing frequency fm is recognized in the competition between the external field and local internal fields, due to magnetostatic, coercive, and eddy current effects. The concept of magnetic object, corresponding to a group of neighboring walls evolving in a highly correlated fashion, is introduced in order to take into proper account the role of short‐range internal correlation fields. With a random spatial distribution of magnetic objects, the dynamic loss is essentially a function of the number n of magnetic objects which are simultaneously active at each value of fm. It is shown that the dynamic balance between applied field and local eddy current counterfields leads, with increasing fm, to a progressive increase of n governed by the simple linear law n=n0+Hexc/V0, where Hexc represents the part of the applied field in excess of the hysteresis and classical contributions. Under these conditions, a ge.
One-dimensional model of the plasma flow in a Hall thruster

A macroscopic model which accounts for the complex interactions between electrostatic, thermal, and kinetic effects in a Hall thruster is presented. The analysis establishes the one-dimensional steady structure of the flow as consisting of an anode sheath, a long electron free-diffusion region, with reverse ion flow, a thin ionization layer, and the acceleration region, which extends into the plume. The ion flow presents a forward sonic point around the exit of the ionization layer, which can be either internal, with a smooth sonic transition, or localized at the channel exit. The supersonic plume is included via a simple expansion model, allowing closure of the formulation and calculation of thruster performance. The results indicate good agreement with experimental data for the case of an internal sonic point, and they delineate the existence and nonexistence regions in the space of externally controllable parameters. They also unveil the importance of the electron pressure, the reverse flow of ions, an.
Deposition of polytetrafluoroethylene films by laser ablation

Films of polytetrafluoroethylene (PTFE) were deposited by laser ablation using the fourth harmonic, at 266 nm, of a Nd‐YAG laser. The films are found to be stoichiometric with the correct optical properties. We suggest that UV absorption onsets the pyrolitic decomposition of PTFE leading to a monomer that subsequently repolymerizes onto a substrate.
Genesis and Development Mechanisms of a Polar Mesocyclone over the Japan Sea

AbstractA polar mesocyclone (PMC) observed over the Japan Sea on 30 December 2010 was studied using a nonhydrostatic mesoscale numerical model with a horizontal resolution of 2 km. The numerical simulation successfully reproduced the observed life cycle of the PMC. The results of the numerical simulation suggest that the life cycle of the PMC may be divided into three stages: an early development stage, in which a number of small vortices appear in a shear zone; a late development stage, which is characterized by the merger of vortices and the formation of a few larger vortices; and a mature stage, in which only a single PMC is present. During the early development stage, vortices are generated in the shear zones of strong updrafts in discrete cumulus convection cells. In contrast, during the late development stage, the vortices develop as a result of barotropic instability in the shear zone. A cloud-free eye and spiral cloud bands accompany the mature stage of a simulated PMC. A warm core structure also .
Analysis of a multi-pump optimization in Raman+EDFA hybrid amplifiers with pump recycling for WDM systems

This paper analyzes multi-pump Raman+EDFA hybrid amplifiers with pump recycling using an improved technique that optimizes the gain and ripple of the amplifier for wavelength division multiplexing (WDM) applications. This technique is based on the equalization of Erbium's gain spectrum by adjusting the flexible gain profile of a multi-pump Raman amplification stage. The residual Raman pump recycled by the Erbiumdoped section is used to increase power pump efficiency. Multi-channel simulated gain characterization of the hybrid amplifier recycling Raman pump, in terms of global gain, ripple, and noise figure, is presented. Different configurations of the Raman stage with single, two, three and four-pump lasers are analyzed. For 8 WDM input channels with two and three-pump lasers, ripple values have presented variation from 3 to 9 dB against 4.3 to 12.6 dB obtained with the previous method, depending on the input power and number of pumps. The ripple analysis have has shown that the proper selection of pump wavelengths and powers, enables the construction of broadband hybrid Raman+EDFA amplifiers with enhanced power conversion efficiency and high and flat gains.
The Geometry of Random Fields

Preface to the Classics edition Preface Corrections and comments 1. Random fields and excursion sets 2. Homogeneous fields and their spectra 3. Sample function regularity 4. Geometry and excursion characteristics 5. Some expectations 6. Local maxima and high-level excursions 7. Some non-Gaussian fields 8. Sample function erraticism and Hausdorff dimension Appendix. The Markov property for Gaussian fields References Author index Subject index.
Concert hall acoustic criteria; subjective significance

The validity of current physical room acoustic criteria developed by various authors in the laboratory has been tested for the first time under the environmental complexity of live concerts. Six independent subjective factors emerged from evaluations on semantic rating scales, namely body, clarity, tonal quality, proximity, spaciousness, and intimacy. In a correlation analysis between subjective factors and measured values of physical room acoustic parameters, the factors clarity and intimacy were not found to be related with any of the physical parameters. The factor body correlated with the ratio of 80‐ms Late‐to‐Early energy, tonal quality with the texture of the impulse response decay, and proximity with the direct‐to‐reverberant energy ratio and distance from platform. Each of the factors body, tonal quality, and proximity were also found to be the effect of an additional objective influence which remained unidentified [A. G. Sotiropoulou, Ph.D. thesis, University of London (1982)]. These results sho.
Direct numerical simulations of transition and turbulence in smooth-walled Stokes boundary layer

Stokes boundary layer (SBL) is a time-periodic canonical flow that has several environmental, industrial, and physiological applications. Understanding the hydrodynamic instability and turbulence in SBL, therefore, will shed more light on the nature of such flows. Unlike its steady counterpart, the flow in a SBL varies both in space and time, which makes hydrodynamic instability and transition from laminar to turbulent state highly complicated. In this study, we utilized direct numerical simulations (DNS) to understand the characteristics of hydrodynamic instability, the transition from laminar to turbulent state, and the characteristics of intermittent turbulence in a smooth SBL for ReΔ in the range of 500–1000. Simulation results show that nonlinear growth plays a critical role on the instability at ReΔ=500 and 600. However, the nonlinear growth does not warrant sustainable transition to turbulence and the outcome is highly dependent on the amplitude and spatial distribution of the initial velocity dist.
Does the ballooning instability trigger substorms in the near‐Earth magnetotail?

The stability of the near-Earth magnetotail against ballooning (or configurational) instability is examined in the framework of the MHD approximation. It is emphasized that a change in plasma pressure induced by a meridional electric field drift δun is an important factor that determines the stability. We have to consider two ways in which plasma pressure changes, that is, a convective change −δun · ▽P0, where P0 is background plasma pressure, and plasma expansion/compression -P0▽ · δun. Since δun is perpendicular to the magnetic field and its magnitude is inversely proportional to the magnetic field strength, δun diverges/converges in usual tail magnetic field configurations. For the instability, the convective change must overwhelm the effects of the plasma expansion/compression. However, near the equator in the near-Earth tail, the latter may overcompensate for the former. We describe the ballooning instability in terms of a coupling between the Alfven and slow magnetosonic waves in an inhomogeneous plasma and derive instability conditions. The result shows that the excessive curvature stabilizes, rather than destabilizes, perturbations. It is also found that the field-aligned flow stabilizes perturbations, as well as the field-aligned current. We infer that under quiet conditions, the plasma pressure gradient in the near-Earth tail is not sharp enough to trigger the instability. The plasma sheet is expected to become more stable during the substorm growth phase because of an increase in the field line curvature associated with the plasma sheet thinning. In the region closer to the Earth, including the ring current, the plasma pressure gradient may be localized in a limited range of the radial distance during the growth phase. However, recently reported plasma and magnetic field parameters before substorm onsets do not provide very convincing evidence that the ballooning instability is the triggering mechanism of substorms.
High-Resolution Observations of Multiwavelength Emissions during Two X-Class White-Light Flares

We observed two X-class white-light flares (WLFs) on 2003 October 29 (~20:40 UT) and November 2 (~17:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76 cm aperture, and the cadence was as high as 2 s. This is the first time that WLFs have been observed in the near-infrared (NIR) wavelength region. We present a detailed study in this paper comparing photospheric continuum observations during the two events with corresponding line-of-sight magnetograms from the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) and hard X-ray (HXR) data from the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). We also discuss several models that provide possible mechanisms to explain these continuum enhancements, especially in the NIR.
The quantum theory of one-electron states at surfaces and interfaces

The matching of the wavefunction at an arbitrary surface is formulated in terms of Green functions. If G1 and G2 are the resolvents for media 1 and 2, respectively, and Gs is the resolvent for a system consisting of 1 and 2 in contact through an interface (not necessarily abrupt), then Gs is fully obtained in terms of G1 and G2. By taking suitable matrix elements one obtains: (i) a secular determinant for the matching eigenvalues (surface states); (ii) a formula for the wavefunction everywhere, and (iii) a formula for the density of states. The case of a film is studied in the same way. The formalism is illustrated with a few examples. This paper deals with the physical information contained in the matrix elements of Gs between points which are either on the surface or else on the same side, but the method yields also the matrix elements across the surface, which are important for the theory of dielectric responses in a system with an interface.
THE WEYL GROUP OF A GRADED LIE ALGEBRA

The action of the group G0 of fixed points of a semisimple automorphism θ of a reductive algebraic group G on an eigenspace V of this automorphism in the Lie algebra g of the group G is considered. The linear groups which are obtained in this manner are called θ-groups in this paper; they have certain properties which are analogous to properties of the adjoint group. In particular, the notions of Cartan subgroup and Weyl group can be introduced for θ-groups. It is shown that the Weyl group is generated by complex reflections; from this it follows that the algebra of invariants of any θ-group is free.Bibliography: 30 titles.
Trapping of quasiparticles of a nonequilibrium superconductor

We have performed experiments where hot electrons are extracted from a normal metal into a superconductor through a tunnel junction. We have measured the cooling performance of such NIS junctions, especially in the cases where another normal metal electrode, a quasiparticle trap, is attached to the superconductor at different distances from the junction in direct metal–to–metal contact or through an oxide barrier. The direct contact at a submicron distance allows superior thermalization of the superconductor. We have analyzed theoretically the heat transport in this system. From both experiment and theory, it appears that NIS junctions can be used as refrigerators at low temperatures only with quasiparticle traps attached.
Semi-Classical Behavior of the Scattering Amplitude for Trapping Perturbations at Fixed Energy

Abstract We study the semi-classical behavior as $h\,\to \,0$ of the scattering amplitude $f(\theta ,\,\omega ,\,\lambda ,\,h)$ associated to a Schrödinger operator $P(h)\,=\,-\,\frac{1}{2}{{h}^{2}}\Delta \,+\,V\,(x)$ with short-range trapping perturbations. First we realize a spatial localization in the general case and we deduce a bound of the scattering amplitude on the real line. Under an additional assumption on the resonances, we show that if we modify the potential $V(x)$ in a domain lying behind the barrier $\left\{ x\,:\,V(x)\,>\,\lambda \right\}$ , the scattering amplitude $f(\theta ,\,\omega ,\,\lambda ,\,h)$ changes by a term of order $\mathcal{O}({{h}^{\infty }})$ . Under an escape assumption on the classical trajectories incoming with fixed direction $\omega $ , we obtain an asymptotic development of $f(\theta ,\,\omega ,\,\lambda ,\,h)$ similar to the one established in the non-trapping case.
Numerical solution for fully developed flow in heated curved tubes

Fully developed laminar flow for a horizontal heated curved tube is studied numerically. The tube is heated so as to maintain a constant axial temperature gradient. A physical model is introduced that accounts for the combined effects of both buoyancy and centrifugal force. Results, for a Prandtl number of one, are presented for a moderate range of Dean numbers and the product of the Reynolds and Rayleigh numbers. Detailed predictions of the flow resistance, the average heat-transfer rate and the secondary-flow streamlines are given. Also presented are results on the position of the local maxima of shear stress and heat-transfer rate. The numerical results reveal that the mass-flow rate is drastically reduced owing to the secondary flow for a given axial pressure gradient. Consequently, the total heat- transfer rate decreases for a more-curved tube as well as for a larger axial temperature gradient. A flow-regime map is provided to indicate the three basic regimes where (i) centrifugal force dominates, (ii) both buoyancy and centrifugal forces are important, and (iii) buoyancy force dominates.
A topological approach to digital topology

YUNG KONG is Associate Professor of Computer Science at Queens College CUNY. He previously held faculty appointments in computer science at Ohio University and in mathematics at City College, CUNY. His main research interest is in topological and geometrical problems of computer graphics and image processing. He received his doctorate in 1986 from the University of Oxford, England, following three years as a graduate student at the Oxford University Computing Laboratory; his thesis, "Digital Topology with Applications to Image Processing," was directed by Dr. A. W. Roscoe and Professor C. A. R. Hoare. His B.A. is in mathematics (with double first class honors) and is from the University of Cambridge, England.
Atlas of animals from the Late Westphalian of Writhlington, United Kingdom

Representative animals from the Writhlington assemblages are collectively illustrated for the first time with notes on palaeoecology, association and distribution. They are from a comparatively well sampled, terrestrial-fresh water fauna of nematodes, bivalvias, arthropods and vertebrates from the Upper Westphalian D of the UK. The Writhlington fauna provides a baseline for comparative faunal work in the Variskan Foreland.