Miracle-dz/UniFAR-FTUs huggingface dataset:
On the equilibrium distribution of the elements in the gas in the Coma cluster

The equilibrium distribution of the elements for the case of an isothermal plasma in a gravitational potential well is given governing equations and a rapidly converging iterative procedure for their solution. Results are applied to the intracluster gas in clusters of galaxies, and implications are identified for the controversy as to whether iron nuclei settle out in the cluster core, and with respect to the interpretation of distribution size and shape for continuum X-ray emission from clusters. A model for the Coma cluster is considered in which the intracluster gas is in equilibrium and partially processed. It is found that this model can account for the angular dependence of the continuum X-ray emission from Coma, as determined by Einstein Observatory observations, at least as well as the uniform composition model.
CCD photometry of the RR Lyrae stars in NGC 4147

Reportamos los resultados de la fotometria CCD a traves de los filtros V y R de las estrellas RR Lyrae conocidas en NGC 4147. Los periodos de todas las variables han sido recalculados y se dan nuevas efemerides. Se detecto efecto Blazhko en las variables V2 y V6. Las estrellas V5, V9 y V15, reportadas previamente como variables, no muestran variaciones. Se reporta la nueva variable, V18, que muestra un periodo de 0.49205 dias y una amplitud de 0.15 mag. Con la tecnica de descomposicion de Fourier de las curvas de luz se han estimado los parametros fisicos de las variables RRab y RRc. El cumulo es del tipo de Oosterhoff I. Los nuevos valores determinados para el contenido de hierro y la distancia; [Fe/H]= -1.22 ± 031 y 16.8 ± 1.3 kpc colocan adecuadamente al cumulo en las secuencias tipo de Oosterhoff-metalicidad y metalicidad-temperatura efectiva para cumulos globulares. Una comparacion con modelos de la Rama Horizontal indica que las RRab de NGC 4147 no han abandonado esa fase aun, lo que es congruente con su periodo promedio y la metalicidad del cumulo
Martin boundaries of cartesian products of markov chains

Let P and Q be the stochastic transition operators of two time-homogeneous, irreducible Markov chains with countable, discrete state spaces X and Y, respectively. On the Cartesian product Z = X x Y, define a transition operator of the form Ra = a·P + (1 — a) · Q, 0 < a < 1, where P is considered to act on the first variable and Q on the second. The principal purpose of this paper is to describe the minimal Martin boundary of Ra (consisting of the minimal positive eigenfunctions of Ra with respect to some eigenvalue t, also called t-harmonic functions) in terms of the minimal Martin boundaries of P and Q.
Phase transitions in a slender cylinder composed of an incompressible elastic material. I. Asymptotic model equation

We present reasons, both experimental and mathematical, for why it is important to consider the radial deformation (thus the lateral traction-free boundary conditions as well) for phase transitions in a slender elastic cylinder. One of the main purposes of this paper is to derive an asymptotic model equation, which takes into account the radial deformation and satisfies the traction-free boundary conditions up to the right order. This is achieved from the three-dimensional field equations through a novel approach that combines a series expansion and an asymptotic expansion. An alternative approach based on Whitham's approach (well used in fluids) is also given. Then, we present some interesting analytic solutions for an infinite cylinder, including those that seem to describe the structure of a phase boundary, the nucleation process and the merge of two-phase boundaries. In particular, by considering the energy distribution based on the nucleation solution, it is revealed that the nucleation process is one of energy localizations, concentrations and separation.
Impacts of Room Temperature on the Performance of a Portable Propane Air Conditioner

The performance of a portable propane air conditioner system, in which the temperatures of the air passing over the condenser and evaporator are equal, has been experimentally investigated under different room temperatures and refrigerant charge levels. The research has been carried out in a range of room temperatures from 20°C to 35°C and in undercharge, standard charge and overcharge conditions. The results show that, at higher room temperatures, the refrigerant temperature in all parts of the system, the density of the refrigerant at the inlet and outlet of the condenser, mass of the refrigerant in the compressor, the mass flow rate of the refrigerant and the cooling capacity of the system in either the undercharge or full charge condition, the specific cooling capacity of the undercharge system, the useful work of the compressor, and the maximum pressure of the refrigerant increase. The increase in room temperature decreases the density of the refrigerant at the inlet and outlet of the capillary tube, the mass of the refrigerant in the capillary tube, the refrigerant subcooling at the inlet of the capillary tube, the maximum velocity of the refrigerant and the coefficient of performance. In addition, the increase in room temperature at overcharge condition causes an increase in the mass flow rate, cooling capacity and specific cooling capacity to a maximum value followed by their decrease. The most important difference between a portable air conditioner and a nonportable system is the increase in cooling capacity with an increase in room temperature in full charge condition.
Efficient Inference in a Random Coefficient Regression Model

Computes a GLS matrix weighted estimator for a panel data set. meangroup.src does a similar estimator, but uses simple weighted average rather than a matrix-weighted average. Swamy(1970), "Efficient Inference in a Random Coefficient Regression Model", Econometrica, vol 38, 311-323. (This abstract was borrowed from another version of this item.)
Three-dimensional optical profilometry for artwork inspection

A special fibre-optic interferometer is proposed for 3D profilometry. Sinusoidal fringes are produced by the interference of two spherical wavefronts emitted from the output fibres of a directional coupler. The fringe pattern is projected on an object surface and the deformed grating image is captured by a CCD camera. Subsequently, the captured image is analysed, and the relationship between the fringe phase and the height distribution of the illuminated surface is derived. The proposed method is simple and accurate. It is suitable for automatic measurements. Detailed theoretical and experimental results are presented. Tests show that the system can detect indents and outdents with a maximum depth of less than 10 µm.
Summation, transformation, and expansion formulas for bibasic series

Etude des extensions a deux bases de la formule de transformation d'Euler et de la formule de developpement de Fields-Wimp. Etablissement d'une formule de transformation a quatre bases independantes, d'une formule d'inversion de Lagrange et de quelques formules de sommation de degres 2, 3 et 4
FINE MAGNETIC FEATURES AND CHIRALITY IN SOLAR ACTIVE REGION NOAA 10930

In this paper, we present fine magnetic features near the magnetic inversion line in the solar active region NOAA 10930. The high-resolution vector magnetograms obtained by Hinode allow detailed analyses around magnetic fibrils in the active region. The analyses are based on the fact that the electric current density can be divided into two components: the shear component caused by the magnetic inhomogeneity and the twist component caused by the magnetic field twist. The relationships between magnetic field, electric current density, and its two components are examined. It is found that the individual magnetic fibrils are dominated by the current density component caused by the magnetic inhomogeneity, while the large-scale magnetic region is generally dominated by the electric current component associated with the magnetic twist. The microstructure of the magnetic field in the solar atmosphere is far from the force-free field. The current mainly flows around the magnetic flux fibrils in the active regions.
Eddy resolving simulations of turbulent solar convection

Deep convection occurs in the outer one‐third of the solar interior and transports energy generated by nuclear reactions to the surface.It leads to a characteristic pattern of time‐averaged differential rotation, with the poles rotating significantly slower (approximately 25 per cent) than the equator. This differential rotation results from Reynolds stresses that are associated with correlations of the longitudinal velocity with the radial and latitudinal velocities. One particularly interesting feature of the solar differential rotation is that it shows significant tilting of angular velocity contours away from the rotation axis (i.e. breaking of the Taylor–Proudman state of rotation rate constant on cylinders aligned with the rotation axis), in contrast to the results from early numerical simulations. In spite of such discrepancies, numerical simulations provide the best chance of making progress in understanding the observations. Many studies have adopted the DNS approach and have justified the artificially large viscosities and thermal diffusivities used as modelling transport by unresolved eddies. LES techniques (which use a turbulence closure to relate transport coefficients to local properties of the flow) offer a superior alternative, but face the problem of defining the turbulence closure, which is potentially difficult in the presence of stratification, rotation and other complicating factors. This problem can be avoided by shifting the responsibility for truncating the turbulent cascade from an explicit turbulence closure to the numerical scheme itself. Since this approach abandons the rigorous notions of the LES approach, we refer to it as a VLES (Very Large Eddy Simulation). This paper compares results of DNS simulations carried out with a spherical‐harmonic code, and preliminary results obtained using a VLES‐type code. Both make the anelastic approximation. Copyright © 2002 John Wiley & Sons, Ltd.
Stress Sensitivity of Piezoelectric Ceramics: Part 2. Heat Treatment

The large rise in permittivity experienced by transducer ceramics when subjected to stress parallel to the polar axis can reduce the utility of these materials. Measurements are described on PZT‐4 and PZT‐8, representative of ceramics useful for high‐power high‐stress applications, for which a stabilizing heat treatment has reduced the change in permittivity. It is shown that the stabilizing effect is permanent. Several stress cycles to 10 or 20 kpsi also stabilize these ceramics. It is shown that the stabilization with stress for stress cycles to 10 kpsi is not permanent. Measurements were made over an aging range from one day to six months.
The 2.5‐D analytical model of steady‐state Hall magnetic reconnection

[1] An analytical model of steady-state magnetic reconnection in a collisionless incompressible plasma is developed using the electron Hall MHD approximation. It is shown that the initial complicated system of equations may be split into a system of independent equations, and the solution of the problem is based on the solution of the Grad-Shafranov equation for a magnetic potential. This equation is found to be fundamental for the whole problem analysis. An electric field potential jump across the electron diffusion region and the separatrices is proved to be the necessary condition for steady-state reconnection. Besides of this fact, it is found that the protons in-plane motion obeys to Bernoulli law. The solution obtained demonstrates all essential Hall reconnection features, namely proton acceleration up to Alfven velocities and the formation of Hall current systems and a magnetic field structure as expected.
Development and application of reduced‐order modeling procedures for subsurface flow simulation

The optimization of subsurface flow processes is important for many applications, including oil field operations and the geological storage of carbon dioxide. These optimizations are very demanding computationally due to the large number of flow simulations that must be performed and the typically large dimension of the simulation models. In this work, reduced‐order modeling (ROM) techniques are applied to reduce the simulation time of complex large‐scale subsurface flow models. The procedures all entail proper orthogonal decomposition (POD), in which a high‐fidelity training simulation is run, solution snapshots are stored, and an eigen‐decomposition (SVD) is performed on the resulting data matrix. Additional recently developed ROM techniques are also implemented, including a snapshot clustering procedure and a missing point estimation technique to eliminate rows from the POD basis matrix. The implementation of the ROM procedures into a general‐purpose research simulator is described. Extensive flow simulations involving water injection into a geologically complex 3D oil reservoir model containing 60 000 grid blocks are presented. The various ROM techniques are assessed in terms of their ability to reproduce high‐fidelity simulation results for different well schedules and also in terms of the computational speedups they provide. The numerical solutions demonstrate that the ROM procedures can accurately reproduce the reference simulations and can provide speedups of up to an order of magnitude when compared with a high‐fidelity model simulated using an optimized solver. Copyright © 2008 John Wiley & Sons, Ltd.
A semi-analytic approach to angular momentum transport in stellar radiative interiors

A novel semi-analytic spectral method, based on eigenfunction expansions, is applied to model the angular momentum transport in stellar radiative interiors. The advantages of our approach are shown by applying it to a spin-down model for a 1M⊙ main-sequence star. The evolution of the coupling between core and envelope is investigated for different values of the viscosity and different geometries and intensities of the poloidal field. We suggest that a quadrupolar poloidal field may explain the short coupling timescale (τc∼10 Myr) needed to reproduce the observed rotational evolution of fast rotators on the zero age main sequence, while a dipolar geometry is indicated in the case of slow rotators (τc∼100 Myr). Our method provides a rigorous analytic treatment of a classic MHD problem and allows us to explore the influence of various parameters on the rotational history of radiative interiors.
Nonlinear stability of field-reversed configurations with self-generated toroidal field

The field-reversed configuration (FRC) is a high-beta compact toroidal plasma confinement scheme in which the external poloidal field is reversed on the geometric axis by azimuthal (toroidal) plasma current. A quasineutral, hybrid, particle-in-cell (PIC) approach [Y. A. Omelchenko and R. N. Sudan, Phys. Plasmas 2, 2773 (1995)] is applied to study long-term nonlinear stability of computational FRC equilibria to a number of toroidal modes, including the most disruptive tilt mode. In particular, a self-generated toroidal magnetic field is found to be an important factor in mitigating the instability and preventing the confinement disruption. This is shown to be a unique FRC property resulting from the Hall effect in the regions of vanishing poloidal magnetic field. The instability-driven toroidal field stabilizes kink formation by increasing the magnetic field energy without destabilizing curvature-driven plasma motion. Finally, the tilt instability saturates due to nonlinear, finite Larmor radius (FLR) effe.
The Bruhat order of the symmetric group is lexicographically shellable

In this note we present an elementary proof that the Bruhat order of the symmetric group S, is lexicographically shellable and hence Cohen-Macaulay. Using a theorem of Verma we obtain as a corollary that LA(Sn), the simplicial complex of chains of S, is a double cone over a triangulation of a sphere of dimension () 2. We will employ the notation and terminology of Bjorner [2]. A finite poset P is said to be bounded if it has a maximum and a minimum element, denoted I and 0 respectively. It is calledpure if all of its maximal chains are the same length and it is graded if it is both bounded and pure. The rank of P is the length of a maximal chain. An element x of a graded poset P has a well-defined rank p(x) equal to the length of an unrefinable chain from 0 to x in P. If P is bounded let P be the poset P {0, 1}. The order complex /\(P) of a poset P is the simplicial complex of all chains in P. A poset is said to be shellable if /\(P) is shellable. For the definition of a shellable complex see [2] or [4]. Similarly P is called Cohen-Macaulay if /\(P) is. See [1], [2] or [6] for the definition and significance of a Cohen-Macaulay complex. Let C(P) be the set of covering relations
Instability of Non-Zonal Baroclinic Flows: Multiple-Scale Analysis

Abstract The linear instability of a non-zonal flow can be reduced to an eigenvalue-eigenfunction problem, governed by a nonseparable partial differential equation (Niehaus, 1980). Approximate solutions, found by the method of multiple scales, are derived here and compared with earlier results found using a spectral method. The amplitude maxima are correctly located. The zonal variations of local wavenumber and of amplitude are qualitatively correct, but not sufficiently extreme. Because the method is oversensitive to local conditions, and less sensitive to global constraints, this comparison provides theoretical limits to the possibility of parametrizing transient eddies in terms of the local time mean state of the atmosphere. The method can be extended easily to flows with more realistic vertical structure.
Applicability of elliptic-relaxation method to free-surface turbulence

The elliptic-relaxation method of Durbin (1993 J. Fluid Mech. 249 465–98), which has had remarkable success in predicting benchmark flows of many different types, is applied to prediction of free-surface turbulence for the first time. An appropriate free-surface boundary condition for the elliptic-relaxation equation is derived by taking account of the balance of dominant terms in the Reynolds-stress transport equation in the vicinity of a free surface. Test calculations for a fully developed turbulent open-channel flow are conducted. The flow consists of two kinds of impermeable boundaries, a solid wall and a free surface, and hence is quite suitable as a new benchmark flow. It is demonstrated that the proposed boundary condition does enable the elliptic-relaxation method to reproduce the correct surface-induced stress anisotropy and that the model properly describes the differences in features between wall-bounded flows and free-surface flows by its main quality in reproducing the non-local blocking effect, a kind of an elementary process of boundary–turbulence interaction. It is also found that the turbulent-transport term plays a central role in characterizing free-surface turbulence, which is therefore quite suitable for critical evaluation of the model performance.
Effects of Temperature and Spectral Irradiance on Performance of Silicon-Based Thin Film Multijunction Solar Cells

A numerical study using Analysis of Microelectronic and Photonic Structures (AMPS) device simulator has been carried out to examine how the operating temperature and spectral irradiance affect the behavior of a hydrogenated amorphous silicon/hydrogenated microcrystalline silicon (a-Si:H/µc-Si:H) tandem cell. We have proposed a new tunnel-recombination junction (TRJ) model to calculate the characteristics of the tandem cell as a complete single device. We have shown that our new TRJ model is reliable and can be used for the simulation of the tandem cell. From the calculated results, we have observed that the performance of the tandem cell is sensitive to the spectral irradiance distribution. Furthermore, we have also observed that the current matching condition slightly affects the temperature coefficient of the tandem cell. We have considered that a top-limited cell has a lower temperature coefficient than the bottom-limited and current-matched cells.
A three-dimensional variational data assimilation system for a climate model: basic scheme and tests

In this study, a scheme of three-dimensional variational data assimilation (3D-Var) is introduced for a grid-point Atmospheric General Circulation Model, developed by the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS-AGCM). The scheme adopts stream function, unbalanced potential velocity, unbalanced geopotential height and relative humidity as analysis variables which are independent of each other. In order to avoid the complexity of background error covariance (B) and reduce the tremendous cost of minimization, variable transform and Conjugate-Gradient Method are used here. Meanwhile, a relationship among multivariable is considered. To test the validity of system and dynamical constraints between mass field and wind field, many experiments including single observation and continuous assimilation added in model are performed, The results show that the relationship among multivariable is reasonable and improvement because of the assimilation is obvious.
Exact modeling for control of flexible manipulators

This work presents the dynamic modeling and active vibration control of planar multilink manipulators having flexible links. Since the eigenvalue problem of such continuous structures is strongly dependent on the posture configuration, at first an efficient matrix formulation is provided in order to derive exact natural frequencies and mode shapes of a robot in its general posture. The analytical modal data are used to develop the forced vibration model; this is accomplished through the analytical decoupling of the modal coordinates of the manipulator; to this latter end, orthogonality conditions of modal shapes sets of planar multilink manipulators are demonstrated. The suppression of vibrations is challenged through a full-state linear quadratic regulator controller by optimally placing collocated sensor/actuator pairs. An optimal stochastic observer is designed in line with the noise-corrupted truncated model, i.e. the continuous Kalman-Bucy filter. The simulation results demonstrate that the presented matrix formulation for deriving exact modal data is effective, and the designed control method, along with the forcedvibration solving strategy, is feasible and efficient.
Colour demosaicking with directional filtering and weighting

Digital cameras usually use a single sensor covered with a colour filter array which samples only one colour at the location of each pixel. Restoring a full-colour image by the demosaicking technique is a key task in the digital imaging pipeline. This study proposes a novel demosaicking approach based on the existing directional filtering and weighting techniques. The contributions of this study are two-fold. First, the authors analyse the advantages and limitations of the existing directional filtering and weighting techniques, and improve the two existing techniques in order to suppress the common demosaicking artefacts. Second, the authors give a new estimated scheme for the reconstruction of the colour components. The experimental results show that the proposed method outperforms the recent six state-of-the-art demosaicking methods in terms of both subjective and objective measures.