Miracle-dz/UniFAR-FTUs huggingface dataset:
Full wave calculations of gravity wave propagation through the thermosphere

Full wave calculations have been performed within the frequency range of gravity waves (10−3 ≤ ω ≤ 10−2 sec−1) for a thermospheric model between 150 and 500 km altitude. In this altitude range gravity waves are coupled with heat conduction waves. Reflection, transmission, conversion, and coupling from one wave type into the other one is described by the elements of the scattering matrix. The dependence of these elements on height and angle of incidence is discussed. The transmission coefficients of gravity waves calculated by full wave theory are compared with simple ray calculations and show that ray treatment is a sufficient approximation for obliquely upward propagating gravity waves and that gravity waves predominate throughout the thermosphere. The thermosphere reacts like a selective filter with respect to upward propagating gravity waves with optimal transmission at kx ∼ ω/C (ω = angular frequency; C = velocity of sound; kx = horizontal wave number).
Superfluidity and the magnetic field of pulsars

The current state of the theory of superfluidity in pulsars is presented. The superfluidity of hadronic matter in neutron stars is considered. It is shown that strong interaction between the neutron and proton condensates leads to a drag current of superconducting protons and to the generation of a strong time-independent magnetic field (B = 1012 G) parallel to the axis of rotation. The strength of this field depends on the microscopic parameters of the superfluid hadrons. Models explaining the origin of glitches and postglitch relaxation are discussed. The coupling time between the neutron superfluid and the rigid crust of the neutron star is calculated.
Sobre o confinamento espacial de sistemas quânticos: o oscilador harmônico unidimensional e o átomo de hidrogênio

In this work we study two types of quantum systems confined in the space limited by a barrier of infinite potential: the unidimensional harmonic oscillator and the hydrogen atom. The two systems are of the great importance in the study of physical properties of quantum systems, such as the vibrational spectrum of molecules in solids and the spectrum of energy for an atom model under pressure. For both systems are obtained analytical solutions to the free and confined situations through the imposition of boundary conditions on the wave function. The energy spectrum of the confined system is obtained by the implementation of computational programs that they research the roots of a polynomial. The obtained results show different effects that happen in confined systems, allowing to do a comparison with free systems.
Electromagnetic extraction of energy from Kerr black holes

When a rotating black hole is threaded by magnetic field lines supported by external currents flowing in an equatorial disc, an electric potential difference will be induced. If the field strength is large enough, the vacuum is unstable to a cascade production of electron-positron pairs and a surrounding force-free magnetosphere will be established. Under these circumstances it is demonstrated that energy and angular momentum will be extracted electromagnetically. As a further consequence it is shown that charge can never contribute significantly to the geometry of a rotating hole. The fundamental equations describing a stationary axisymmetric magnetosphere are derived and the details of the energy and angular momentum balance are discussed. A perturbation technique is developed which can be used to provide approximate solutions for slowly rotating holes. Solutions appropriate when the field lines threading the hole lie on conical and paraboloidal surfaces at large distances are described to illustrate this mechanism. These ideas are incorporated into a discussion of a model of active galactic nuclei containing a massive black hole surrounded by a magnetized accretion disc. In this model relativistic electrons can be accelerated at large distances from the hole and therefore will not incur serious losses, which is a defect of some existing models. In addition, if the field lines have paraboloidal shape, the energy will be beamed along antiparallel directions as observations of both compact and extended radio sources seem to require.
Development of modified embedded atom potentials for the Cu–Ag system

Abstract The modified embedded atom method is tested in the atomistic simulations of binary fcc metallic alloys. As an example the alloying behaviour of Cu–Ag is studied using the molecular dynamics (MD) method. The MD algorithms that we use are based on the extended Hamiltonian formalism and the ordinary experimental conditions are simulated using the constant-pressure, constant temperature (NPT) (MD) method. The enthalpy of mixing values of the random Ag–Cu binary alloys are obtained as functions of concentration after 20 000 steps.
Stress work effects in laminar flat-plate natural convection

The effects of both viscous and pressure stress work are considered in laminar natural convection on flat surfaces. Whereas in previous investigations only viscous stress work effects were studied, it is established here that pressure work effects are generally rather more important both for gases and liquids. Variations in the properties of the fluid outside the natural convection boundary layer are shown to occur inevitably in this problem and are found to lead to effects comparable with those produced by pressure work. Property variations in the boundary layer itself are also found to be of importance. Such variations, both inside and outside the boundary layer, have been ignored in previous studies. Examples of flows are discussed in which the fluids are either perfect gases or fluids undergoing small changes in temperature and pressure. For both of these fluids, the effects of conditions of either constant temperature or constant entropy in the fluid outside the boundary layer are examined.
Study on an Infrared Image Enhancement Algorithm by Using Lateral Inhibition of Human Visual System

Aiming at infrared images' disadvantages such as low contrast and blur edges, an infrared image enhancement algorithm using lateral inhibition of human visual system (HVS) is proposed. The algorithm makes use of the rapid decline properties of exponential function to reconstruct lateral inhibition coefficient distribution model based on exponential function, which could provide an obvious inhibition function and produce strong contrast between sharp edge and even part. The experimental results show that image edges are obviously highlighted, and the edge enhancement is 2 times compared with traditional balanced spacing density of gray-scale, and the PSNR is 2 times compared with traditional histogram equalization method.
Optimal Trajectory Planning of Manipulators With Collision Detection and Avoidance

This article presents an optimal trajectory-planning method for robot manipulators with collision detection and avoidance. The obstacles and robot segments are represented by a set of convex polyhedra. The collision detection is performed at each discretized robot configuration by an efficient procedure devel oped with the computational geometry method, which computes a distance function of the robot segments and the obstacles. By introducing this function for specifying the collision-free con straint, the path-planning problem is formulated as an optimal control problem using the augmented Lagrangian, which may be considered as a combination of the duality, penalty and con straint relaxation methods. The problem is solved by a robust UZAWA-like algorithm, where a subgradient method is applied for the primal optimization, as the distance function is not ev erywhere differentiable. An example is given for the trajectory planning of a robot arm with three revolute joints.
The experimental synthesis of random pressure fields: Methodology

This paper presents a methodology for the off-line reproduction of random pressure fields with given spatial correlation characteristics. The simulation method is first presented, together with an outline of the signal processing techniques required. The design of an experimental setup is then detailed in relation with the nature of the simulated pressure fields. Of particular interest is the laboratory synthesis of three different types of partially correlated random excitations: an acoustic diffuse field, a grazing incident plane wave, and a turbulent boundary layer. The corresponding excitations are generated in a semianechoic chamber over a test panel using a near-field array of 16 loudspeakers driven by a set of optimal signals. The loudspeakers are positioned at a suitable distance above a sufficiently dense grid of microphones close to the simulation surface. The mutually correlated drive signals are determined from both the target correlation properties and the acoustic transfer functions measured.
Cosmic-ray transport and acceleration. I - Derivation of the kinetic equation and application to cosmic rays in static cold media. II - Cosmic rays in moving cold media with application to diffusive shock wave acceleration

The propagation of energetic charged particles in a zero electric field and an ordered uniform magnetic field (B0) in a cold background medium is investigated theoretically, with a focus on the case where Alfven waves propagating parallel or antiparallel to B0 are superposed. The derivations of the governing equations of a quasi-linear theory for pitch-angle and momentum diffusion and for its applications to cosmic-ray protons in a cold medium at rest or in nonrelativistic motion parallel to B0 are given in great detail; numerical predictions are presented in tables and graphs and discussed with reference to published observational data. 83 references.
Analyzing Relations in Dyads

This article deals with the application of regression models to observations on relations in dyads. I address three problems that have troubled past investigations of this sort: (1) how to incorporate measures of nodal characteristics into models explaining ties in dyads, (2) how to specify and estimate the effects of reciprocity, and (3) how to measure and control auto-correlation arising from dyads having common nodes. A model is developed that is designed to overcome these problems. An illustration is then provided via an analysis of data on interorganizational relations. The analysis yields empirical results that suggest the potential of these methods for testing certain social network theories.
Parametric loudspeaker for speech signal based on the combination of amplitude and frequency modulations

A parametric loudspeaker has been used for audio guidance to a specific area because it has a sharper directivity compared with the conventional electrodynamic loudspeakers. The parametric loudspeaker emits an ultrasound as a carrier wave, which is modulated with an audio signal and has large-amplitude. An audible sound is reproduced by the modulated ultrasound with large-amplitude distorted by the nonlinearity on the air. The conventional modulations have been proposed as the amplitude modulation and the frequency modulation. In the sound quality, the amplitude modulation is superior to the frequency modulation. However, in the sound pressure level, the frequency modulation is superior to the amplitude modulation. In the present paper, we especially focus on that the parametric loudspeaker will emit the speech signals for the audio guidance. Therefore, we propose new modulation method based on the combination of amplitude and frequency modulations, which are specialized for speech signals. More specifica.
Superfluid hydrodynamics in rotating neutron stars. I - Nondissipative equations. II - Dissipative effects

Newtonian hydrodynamic equations are developed which describe the outer-core regions of neutron stars composed of superfluid neutrons, superconducting protons, and degenerate electrons and muons. The equations include couplings to the gravitational and electromagnetic fields. They also include the effects of rotation and forces due to the elastic properties of the neutron and proton vortices. The set of equations is closed by constructing a model of the total energy density and using it to express the dependent variables in terms of the independent variables. The low-frequency-long-wavelength limit of the equations is determined.
Mergers and Starbursts at Large Redshifts: The Case of 3C 368

The results of a multiwavelength study of the high-redshift radio galaxy 3C 368, which has optical and spectroscopic properties perhaps typical of powerful 3CR galaxies at large redshifts, are reported. The galaxy's resolved, multicomponent morphology of the starlight continuum and forbidden O II 3727 A emission-line gas and the properties of the ionized-gas velocity field are suggestive of a strong and highly dissipative merger. The morphological and spectroscopic similarities with other 3CR galaxies at redshift greater than one suggest that spectacular merging was a common process in such systems at early epochs. 40 references.
The generation of capillary instabilities on a liquid jet

The coupling between imposed disturbances and capillary instabilities on a liquid jet is examined. It is shown that in most physical situations the forcing produces neutral waves which can then turn into growing waves as the profile relaxes or may be amplified nonlinearly by a mechanism of the type considered by Akylas & Benney (1980). The effectiveness of the coupling is expressed quantitatively by numerically computed values of the ‘coupling coefficient’.
On Variograms in Point Process Statistics

Variograms, which are frequently used in geostatistics, are of value also in the statistics of marked point processes. When the marks come from a random field which is independent of the point process, ideas of geostatistics suffice for the interpretation of point process variograms. When this model is not appropriate, interactions between the points lead to point process variograms having forms which are unusual in geostatistics. This is shown by three theoretical examples and one from forestry.
Arctic Warming Induced by Tropically Forced Tapping of Available Potential Energy and the Role of the Planetary-Scale Waves

AbstractOne of the challenging tasks in climate science is to understand the equator-to-pole temperature gradient. The poleward heat flux generated by baroclinic waves is known to be central in reducing the equator-to-pole temperature gradient from a state of radiative–convective equilibrium. However, invoking this relationship to explain the wide range of equator-to-pole temperature gradients observed in past climates is challenging because baroclinic waves tend to follow the flux–gradient relationship such that their poleward heat flux is proportional to the equator-to-pole temperature gradient and zonal available potential energy (ZAPE). With reanalysis data, the authors show the existence of poleward heat transport by planetary-scale waves that are independent of the flux–gradient relationship and baroclinic instability. This process arises from a forced tapping of atmospheric ZAPE by planetary-scale waves that are triggered by enhanced tropical convection over the Pacific warm pool region. The Rossby.
Recovering facular areas through Doppler imaging

Similar to the Sun, stellar active regions appear to consist of dark spots in combination with surrounding bright facular regions. The present study uses the Doppler imaging technique to recover the stellar surface structures from simu- lated spectral observations obtained from a given theoretical stellar surface. The objective of the study is to investigate how the recovered surface structure depends on observing parameters such as rotational phase coverage, choice of spectral lines, signal-to-noise ratio, and projected equatorial rotational velocity. The inversions demonstrate that those stellar surface active regions with high temperature contrast in both longitudinal and latitudinal directions can be satisfactorily reproduced using Doppler imaging. Observations must, however, fulfill such strict conditions that a complete reconstruction is somewhat unreal- istic. Nevertheless, in a more realistic example, the hot facular areas result in quite distinct and easily recognizable features on the stellar surface map, even though they are not completely reconstructed.
Advantages of Silicon Nanowire Metal–Oxide–Semiconductor Field-Effect Transistors over Planar Ones in Noise Properties

We have investigated the low-frequency noise behavior of silicon nanowire metal–oxide–semiconductor field-effect transistors (NWFETs) by comparison with that of a planar FET. We have found that the NWFET exhibits lower noise intensity than the planar FET. By analyzing the factors influential to noise intensity, one of the most possible origins of this advantage of the NWFET results from the electron distribution in the channel in NWFET. Owing to quantum confinement, the position of charge-centroids in the channel of NWFET is located further from the interface, resulting in the lower trapping probability between the electrons and oxide traps. These results clearly demonstrate the advantage of three-dimensional structures in static and noise properties.
What is the Least Expected Number of Real Roots of a Random Polynomial

Let $G_n$ be a random polynomial with coefficients. Denote by ${\cal N}(G_n)$ the number of real roots of $G_n$. We find the minimum of $\sup_{n\in{\bf N}}{\bf E}{\cal N}(G_n)$ over different classes of coefficient distributions.
Spin-Orbit Interaction Effects on the Rosseland Mean Opacity

Recently published opacity tables for astrophysical mixtures using the OPAL code showed significant differences when compared to the commonly used Los Alamos results. An important finding of the OPAL calculations was a large opacity enhancement (approximately factors of 3) in the few hundred-thousand degree temperature range. This new opacity bump is a consequence of improvements in the atomic data generation
THOMAS-FERMI METHOD FOR COMPUTING THE ELECTRON SPECTRUM AND WAVE FUNCTIONS OF HIGHLY DOPED QUANTUM WIRES IN N-SI

The application of Thomas - Fermi method to calculate the electron spectrum in highly doped n-Si quantum wires is presented under finite temperatures, where the many-body effects, like exchange, are taken into account. The electron potential energy is calculated from a single equation. Then the electron energy sub-levels and wave functions within the potential well are simulated from the Schrodinger equation. For axially symmetric wave functions the shooting method has been used. Two methods have been applied to solve the Schrodinger equation in the case of the anisotropic effective mass, the variation method and the iteration procedure for the eigenvectors of the Hamiltonian matrix.
Hall mobility and free electron density at the SiC/SiO2 interface in 4H–SiC

The electron mobility and free electron density have been measured in 4H– and 6H–SiC metal-oxide-semiconductor inversion layers using the Hall effect. The 4H–SiC inversion layers are found to have very poor conductance which is caused by severe trapping of electrons at the Si/SiO2 interface. The trapping causes reduced conductance through a reduction in the number of free electrons in the inversion layer, and also because of a drop in the mobility due to increased Coulombic scattering.
CHECKING LINEAR RESPONSE THEORY IN DRIVEN BISTABLE SYSTEMS

The validity of linear response theory to describe the response of a nonlinear stochastic system driven by an external periodical time dependent force is put to a critical test. A variety of numerical and analytical approximations is used to compare its predictions with numerical solutions over an extended parameter regime of driving amplitudes and frequencies and noise strengths. The relevance of the driving frequency and the noise value for the applicability of linear response theory is explored for single and multi-frequency input signals.
DNA sensing using split-ring resonator alone at microwave regime

In this paper, the feasibility of utilization of a single element double split-ring resonator as a biosensing device has been demonstrated. The compact resonator has been excited by time-varying magnetic fields generated from the 50 Ω microstrip transmission line. In this work, DNA hybridization is recognized with shift in S21 resonant frequency. When thiol-linked single stranded-DNA is immobilized onto a gold (Au) surface and is then coupled with complementary-DNA, the frequency changes by Δfss-DNA=20 MHz and Δfhybridization=60 MHz, respectively. Thus, it is clear that the resonator can be utilized as a DNA sensing element in the microwave regime.
An adaptive filter for the construction of the Planck Compact Source Catalogue

We develop a linear algorithm to extract extragalactic point sources for the Compact Source Catalogue of the upcoming Planck mission. This algorithm is based on a simple top-hat filter in the harmonic domain with an adaptive filtering range which does not require a priori knowledge of the cosmic microwave background power spectrum, and experimental parameters such as the beam size and shape or the pixel noise level.
Downregulation of barley ferulate 5-hydroxylase dramatically alters straw lignin structure without impact on mechanical properties

Barley is a major cereal crop for temperate climates, and a diploid genetic model for polyploid wheat. Cereal straw biomass is an attractive source of feedstock for green technologies but lignin, a key determinant of feedstock recalcitrance, complicates bio-conversion processes. However, manipulating lignin content to improve the conversion process could negatively affect agronomic traits. An alternative approach is to manipulate lignin composition which influences the physical and chemical properties of straw. This study validates the function of a barley ferulate 5-hydroxylase gene and demonstrates that its downregulation using the RNA-interference approach substantially impacts lignin composition. We identified five barley genes having putative ferulate 5-hydroxylase activity. Downregulation of HvF5H1 substantially reduced the lignin syringyl/guaiacyl (S/G) ratio in straw while the lignin content, straw mechanical properties, plant growth habit, and grain characteristics all remained unaffected. Metabolic profiling revealed significant changes in the abundance of 173 features in the HvF5H1-RNAi lines. The drastic changes in the lignin polymer of transgenic lines highlight the plasticity of barley lignification processes and the associated potential for manipulating and improving lignocellulosic biomass as a feedstock for green technologies. On the other hand, our results highlight some differences between the lignin biosynthetic pathway in barley, a temperate climate grass, and the warm climate grass, rice, and underscore potential diversity in the lignin biosynthetic pathways in grasses.
Spin–Orbit Interaction in the Tight-Binding Model —Toward the Comprehension of the Rashba Effect at Surfaces—

The linear combination of atomic orbitals (LCAO) tight-binding approach is adopted to obtain spin–orbit interaction at surfaces leading to the Rashba effect. Starting from the Dirac equation, the spin–orbit interaction is given by the nonrelativistic limit. All terms, i.e., intra-atomic L · S, and spin-flipping transfer matrix elements, are obtained. The tight-binding Hamiltonian is diagonalized resulting in the spin-splitting energy bands for a one-dimensional atomic chain and a two-dimensional triangular atomic sheet. The spin textures induced by the Rashba effect are also revealed.
Fully developed anisotropic hydromagnetic turbulence in interplanetary space

The solar-wind magnetohydrodynamic turbulence is observed to be made mainly of Alfvenic fluctuations propagating away from the sun. It is shown that such an asymmetric state is a general consequence of the evolution of developed magnetohydrodynamic turbulence, which, starting from an initial asymmetry between modes with cross helicity +1 and -1, tends, as a consequence of nonlinear interactions, towards a state where the only modes left are those initially prevailing (with either cross helicity +1 or -1).