Miracle-dz/UniFAR-FTUs huggingface dataset:
Anisotropic mesh adaptation: towards user‐independent, mesh‐independent and solver‐independent CFD. Part I: general principles

The present paper is the lead article in a three-part series on anisotropic mesh adaptation and its applications to structured and unstructured meshes. A flexible approach is proposed and tested on two-dimensional, inviscid and viscous, finite volume and finite element flow solvers, over a wide range of speeds. The directional properties of an interpolation-based error estimate, extracted from the Hessian of the solution, are used to control the size and orientation of mesh edges. The approach is encapsulated into an edge-based anisotropic mesh optimization methodology (MOM), which uses a judicious sequence of four local operations: refinement, coarsening, edge swapping and point movement, to equi-distribute the error estimate along all edges, without any recourse to remeshing. The mesh adaptation convergence of the MOM loop is carefully studied for a wide variety of test cases
Identification and Estimation in Binary Choice Models with Limited (Censored) Dependent Variables

In this paper, a class of statistical models which generate simultaneous equation models with both discrete and continuous endogenous variables is introduced. This class of models can also be regarded as a new class of switching simultaneous equation models which are of general interest. Identification and estimation problems are investigated. Several simple consistent two stage methods are proposed. The consistency of those estimators is proved. Two step maximum likelihood procedures are then developed.
Evaluation of explicit algebraic stress models using direct numerical simulations

The paper deals with evaluation and improvement of two recent explicit algebraic turbulent stress models (EASMs). The first model was derived by Gatski and Rumsey (2001 Closure Strategies for Turbulent and Transitional Flows ed B E Launder and N D Sandham (Cambridge: Cambridge University Press) pp 9–46) and the second is the one devised by Wallin and Johansson (2000 J. Fluid Mech. 403 89–132). These models are studied for the turbulent flow through a square duct which involves a secondary flow and significant anisotropy between the turbulent Reynolds stress tensor components. An a priori evaluation of these models is made using direct numerical simulation (DNS) results of Navier–Stokes equations. In order to handle wall proximity effects, a damping function is suggested. The material frame-indifference (MFI) of these models is studied using the eigenvectors of the rate-of-deformation tensor and their angular velocities. This procedure allows us to evaluate an objective vorticity tensor. For this flow, it .
On some parameters related to weak noncompactness in L1(μ,E)

Abstract A weak measure of noncompactness γU is defined in a Banach space in terms of convex compactness. We obtain relationships between the measure γU (A) of a bounded set A in the Bochner space L1 (μ,E) and two parameters Π(A) and Δ1(A). Then the criterion for relative weak compactness due to Ülger [19] and Diestel-Ruess-Schachermayer [11] is recovered.
First-principles study of the electronic and optical properties in rhombohedral LaAlO3

In this paper, the electronic structure, chemical bonding, and optical properties of rhombohedral LaAlO3 are investigated by using the full potential linearized augmented plane wave method with the generalized gradient approximation. The analysis of the electronic density profile, Mulliken charge, and bond population shows a combination of the covalent and ionic natures in the chemical bonding. The calculated complex dielectric function is consistent with the experimental data from the ultraviolet spectroscopic ellipsometry measurement. The optical spectra are assigned to the interband transition from O valence to La conduction bands in the low energy region. Furthermore, absorption spectrum, electron energy-loss spectrum, optical conductivity, reflectivity, and refractive index are derived from the complex dielectric function, and the absorption spectrum exhibits an optical band gap of 6.1 eV, which is consistent with several other experimental measurements.
The self-attraction correction for the FG5X absolute gravity meter

The gravitational attraction of the body of a gravity meter upon its own proof mass is sometimes called the self-attraction. The self-attraction is a source of systematic error for absolute measurements of g, the acceleration of an object due to Earth's gravity. While the effect is typically small—of the order of one part per billion of the Earth's gravitational attraction—it is significant at the current level of accuracy of absolute gravity meters. In the past, a self-attraction correction for the FG5 gravity meter has been estimated by considering a rather coarse description of the instrument using simple geometrical shapes (spheres and cylinders). This paper describes a more complete calculation using a CAD-based digitized model of the newest FG5X instrument. We have also included the attraction of the co-moving drag-free chamber as well as the self-attraction of the counterweights used in the FG5X to reduce recoil. The results are also applicable to older style FG5 instruments with a fibre-optic interferometer base. The correction found with this new approach agrees with previous estimates but is now based upon a more complete and accurate model.
Resistivity and Temperature Coefficient of Thin Metal Films with Rough Surface

The thickness dependence of resistivity and its temperature coefficient of thin metal films has been studied. A theory is proposed to include, the surface roughness in determining the film resistivity, in addition to the reduced mean free path to conduction electrons. The ratio of the roughness to the mean free path, h/λ, is introduced as a convenient parameter. The thickness dependence of the resistivity predicted by the present theory agrees with the well known Fuchs-Sondheimer theory if h/λ=0. If h/λ>0, the discrepancy between the two theories increases with the decrease in film thickness. Satisfactory agreement between the theoretical and experimental results can be obtained by adjusting the value of h/λ.
Modeling the effects of ionospheric oxygen outflow on bursty magnetotail flows

Using a global multifluid MHD model, we demonstrate the effects of magnetospheric O+ on bursty magnetotail flows. We carry out two simulations without ionospheric outflow to use as baseline, one driven by real solar wind data and one driven by idealized solar wind. Solar wind data from 1 October 2001 are used as a storm time solar wind driver. During this event, the plasma sheet was observed to be rich in O+, making the event of interest for a model analysis of the effects of ionospheric origin O+ on magnetospheric dynamics. We carry out outflow comparison simulations for both the realistic and idealized solar wind drivers using a simple empirical model that places auroral outflow in regions where downward propagating Poynting flux and electron precipitation are present, combined with a low‐flux thermal energy O+ outflow over the entire polar region. We demonstrate the effects of O+ on magnetotail structure and the occurrence rate and strength of bursty, fast earthward flows. The addition of O+ to the magnetotail stretches the tail and increases the velocity of bursty earthward flows. This increase is shown to be produced by reconnection events in an extended current sheet created by tail stretching.
Evaluation of the filtered leapfrog-trapezoidal time integration method

An analysis and evaluation are presented for a new method of time integration for fluid dynamic proposed by Dietrich. The method, called the filtered leapfrog-trapezoidal (FLT) scheme, is analyzed for the one-dimensional constant-coefficient advection equation and is shown to have some advantages for quasi-steady flows. A modification (FLTW) using a weighted combination of FLT and leapfrog is developed which retains the advantages for steady flows, increases accuracy for time-dependent flows, and involves little coding effort. Merits and applicability are discussed.
Plasma wave simulation based on a versatile finite element method solver

The possibility of plasma wave simulation based on the finite element method (FEM) was explored, and a new full wave simulation code of the lower hybrid (LH) wave, Lower Hybrid wavE Analysis based on FEM (LHEAF), was developed. The efficient iterative solver for the LH wave [O. Meneghini, S. Shiraiwa, and R. Parker, Phys. Plasmas 16, 090701 (2009)] was coupled to one-dimensional Fokker–Planck calculation to obtain the self-consistent distribution function. In LHEAF, seamless handling of the core, scrape off layer, and antenna regions were realized and the wave launching structure were naturally included into the simulation. Simulation results of a Maxwellian tokamak plasma showed good agreement with ray tracing calculations and the TORIC-LH spectral solver [J. C. Wright, P. T. Bonoli, A. E. Schmidt et al., Phys. Plasmas 16, 072502 (2009)]. Compared to spectral domain solvers, the computational requirements are reduced significantly, allowing an Alcator C [M. Porkolab, J. J. Schuss, B. Lloyd et al., Phys. .
A Thermodynamic Equilibrium Climate Model for Monthly Mean Surface Winds and Precipitation over the Tropical Pacific

Abstract Diagnosis of the dynamic and thermodynamic balances using observed climatological monthly mean data reveals that 1) anisotropic, latitude-dependent Rayleigh friction coefficients lead to much improved modeling of the monthly mean surface wind field for a given monthly mean sea level pressure field, and 2) the annual variation of the vertically averaged lapse rate is important for modeling sea level pressure. Based on the aforementioned observations, a thermodynamic equilibrium climate model for the tropical Pacific is proposed. In this model, the sea level pressure is thermodynamically determined from sea surface temperature (SST) through a vertically integrated hydrostatic equation in which the vertical mean lapse rate is a function of SST plus a time-independent correction. The surface winds are then computed from sea level pressure gradients through a linear surface momentum balance with anisotropic, latitude-dependent Rayleigh friction coefficients. The precipitation is finally obtained from .
A Comparison of the Accuracy of Three Anelastic Systems and the Pseudo-Incompressible System

Abstract The accuracy of three anelastic systems (Ogura and Phillips; Wilhelmson and Ogura; Lipps and Hemler) and the pseudo-incompressible system is investigated for small-amplitude and finite-amplitude disturbances. Based on analytic solutions to the linearized, hydrostatic mountain wave problem, the accuracy of the Lipps and Hemler and pseudo-incompressible systems is distinctly superior to that of the other two systems. The linear dispersion relations indicate the accuracy of the pseudo-incompressible system should improve and the accuracy of the Lipps and Hemler system should decrease as the waves become more nonhydrostatic. Since analytic solutions are not available for finite-amplitude disturbances, five nonlinear, nonhydrostatic numerical models based on these four systems and the complete compressible equations are constructed to determine the ability of each “sound proof” system to describe finite-amplitude disturbances. A comparison between the analytic solutions and numerical simulations of th.
A BAW antenna duplexer for the 1900 MHz PCS band

Miniature antenna duplexers are used in modem cellular telephone handsets. We present a new solution utilizing micro-machined, thin Film Bulk Acoustic Resonators (FBAR). A 1900 MHz duplexer with dimensions 5/spl times/8/spl times/2 mm is achieved. The duplexer, a three port device, achieves low loss from transmitter (Tx) to antenna (Ant) ports with a filter at 1880 MHz and from Ant to receiver (Rx) ports with a filter at 1960 MHz. High isolation from Tx to Rx port is achieved by coupling the two filters with a quarter wavelength line. Filter bandwidth is /spl sim/3%. The filters are realized as 21/2 or 31/2 section ladder connected FBARs with the shunt FBARs tuned 3% lower in frequency than the series FBARs to provide a flat pass band. Individual FEAR resonators are free membranes formed of Aluminum Nitride piezoelectric and metal electrode films micro-machined on a silicon substrate. Resonators with electro-acoustic coupling k/sub t//sup 2//spl sim/3 to 5% and Q/spl sim/300 are achieved. Filters fabricated in this manner achieve minimum insertion loss /spl sim/1 dB, out-of-band rejection of /spl sim/20 dB, 60 MHz bandwidth, and an input power capability of 2 Watts. Duplexers are assembled from one each Tx and Rx filter, and a lumped /spl lambda//4 line of two inductors and a capacitor. These duplexers have insertion loss <2 dB in the pass bands, and Tx to Rx isolation >45 dB.
Experimental observations of spontaneous breaking of reflectional symmetry in turbulent flow

A unique experimental facility along with unique methods of measurement of vorticity, helicity and related quantities were used in order to obtain the following main results. Strong experimental evidence in favour of the existence of the phenomenon of spontaneous reflectional symmetry breaking (SRSB) in turbulent flows with initial and boundary conditions, which are nominally reflectionally symmetrical. In contrast to widespread expectation, this SRSB is exhibited not only in production of nonzero mean helicity, but in a number of more subtle effects related to spectrally and spatially localized SRSB. We observed qualitatively different cases of SRSB exhibited in large and small scales separately and concomitantly with helicity of different signs at different scales and, in particular, cases with SRSB and vanishing mean helicity. Finally, in some cases the flow was almost perfectly reflectionally symmetrical, possessing an almost vanishing cospectrum. A surprisingly strong variability of this phenomenon was observed in contrast with ‘conventional‘ characteristics, which exhibited regular behaviour. On the basis of a large number of different results our conclusion is that the variability of parameters characterizing SRSB is an intrinsic property at least of some turbulent flows.
Modification of PP and Its Application

In order to find a more effective method of solving the problem of subjectivity and difficulty to deal with the high-dimension data, an improved Projection Pursuit (PP) based on Particle Swarm Optimization (PSO) was introduced. The PSO algorithm was employed to optimize the function of the projected indexes in the PP. Application results show the efficiency of the modification. This study has significance in theory and practice for the related research.
Selective smoothed finite element methods for extremely large deformation of anisotropic incompressible bio‐tissues

Two dynamic selective smoothed FEM (selective S‐FEM) are proposed for analysis of extremely large deformation of anisotropic incompressible bio‐tissues using the simplest four‐node tetrahedron elements. In the present two Selective S‐FEMs, the method that consists of the face‐based smoothed FEM (FS‐FEM) used for the deviatoric part of deformation and the node‐based smoothed FEM (NS‐FEM) used for the volumetric part is called FS/NS‐FEM; another method that replaces the deviatoric part of deformation in the first one by the edge‐based smoothed FEM (3D‐ES‐FEM) is call 3D‐ES/NS‐FEM. Both selective S‐FEMs can achieve outstanding accuracy, and stability of volumetric locking free. This is because the NS‐FEM offers an ‘overly‐soft’ feature (in contrast to the standard FEM ‘overly‐stiff’ model), which can be used to effectively mitigate the volumetric locking, and on the other hand, the 3D‐ES‐FEM and FS‐FEM produce close to exact stiffness for the discretized model leading to accurate solution. Numerical examples are presented to examine the performance of the selective S‐FEM methods, including soft bio‐tissues that may be isotropic, transversely isotropic, and anisotropic arterial layered materials. The present methods are found having good accuracy and performance. The examples also demonstrate that the proposed methods are very robust and possess remarkable capabilities of handling element distortion, which is very useful for simulating soft materials including bio‐tissues. Copyright © 2014 John Wiley & Sons, Ltd.
The Presence of Helium in Hot DA White Dwarfs: The Role of Radiative Levitation and the Case for Stratified Atmospheres

The role of helium radiative levitation in the envelopes of hot DA white dwarfs is examined. Explicit time-dependent calculations of helium diffusion in the presence of radiative support carried out in evolving DA models show that the helium distribution in the outermost layers of the models relaxes rapidly to a configuration corresponding to diffusive equilibrium. Observations of these regions show only equilbrium helium abundances and are totally decoupled from the evolving internal helium profile. It is shown that the helium abundances supported by radiative forces in the atmospheric layers of these stars are too small to account for the observations. It is suggested that a mechanism other than radiative levitation must be used to compete against gravitational settling in these stars. A number of mechanisms are discussed and it is concluded that an equilibrium between ordinary diffusion driven by a composition gradient and settling may be the best possibility. The implications of this model are discussed in detail. 66 references.
Vibration of otolithlike scatterers due to low frequency harmonic wave excitation in water.

Otoliths may be approximated as hard objects moving in an acoustic medium in response to arriving sounds. We modeled how parameters of sound such as frequency and direction could be encoded from the motion of the otoliths. Prior numerical models predicted harmonic oscillation (rocking) of scatterers suspended in an acoustic medium when exposed to planar harmonic waves. Because of the potential for the angular oscillation to produce additional information about the sound source, the simulated rocking motions were studied using an additional numerical model. The number of scatterers, their spatial arrangements, shapes, and the characteristics of the incident sound waves were varied. The results were analyzed and will be presented. [Work supported by the Office Naval Research. ]
Impact Oscillator Model for the Prediction of Dynamic Cushion Curves of Open Cell Foams

Cushion curves enable packaging designers to optimize a design solution for a given product fragility and expected distribution environment drop height. The industry accepted techniques for developing these curves are time intensive and devoid of a physical understanding of the materials and the physics involve in energy absorption. This paper delves into a qualitative understanding of the dynamics of a platen impacting an open cell foam cushion material. An hyperelastic material model is used to describe the foam's nonlinear stress–strain relationship, while its damping and hysteretic behaviour are represented with linear viscoelasticity. Using a simple nonlinear, discontinuous model of a drop test along with numerical simulations, the study examines the physics of the impact. The numerical studies show that the model is able to provide predictions of the shock pulse's shape, duration and amplitude at various static stresses and drop heights. The dynamic cushion curves generated by the model retain the characteristic concave upward ‘trough’ shape of the experimental curves. Furthermore, the model shows that the optimal amplitude of shock absorbed for a given set of drop conditions depends on the foam's thickness and cross‐sectional area. Lastly, the model is validated using the comparison of a predicted curve and experimental data captured using a cushion tester. Copyright © 2014 John Wiley & Sons, Ltd.
Electro-caloric effect in lead-free Sn doped BaTiO3 ceramics at room temperature and low applied fields

Structural, dielectric, ferroelectric (FE), 119Sn Mossbauer, and specific heat measurements of polycrystalline BaTi1–xSnxO3 (x = 0% to 15%) ceramics are reported. Phase purity and homogeneous phase formation with Sn doping is confirmed from x-ray diffraction and 119Sn Mossbauer measurements. With Sn doping, the microstructure is found to change significantly. Better ferroelectric properties at room temperature, i.e., increased remnant polarization (38% more) and very low field switchability (225% less) are observed for x = 5% sample as compared to other samples and the results are explained in terms of grain size effects. With Sn doping, merging of all the phase transitions into a single one is observed for x ≥ 10% and for x = 5%, the tetragonal to orthorhombic transition temperature is found close to room temperature. As a consequence better electro-caloric effects are observed for x = 5% sample and therefore is expected to satisfy the requirements for non-toxic, low energy (field) and room temperature b.
Sci-Fri PM Imaging-01: Comparison of POCS and cTERA Image Reconstruction Algorithms Applied to 3D Sparsely Sampled k-Space Data

Real‐time 3D magnetic resonance(MR)imaging sometimes focus on rapid data acquisition by full sampling the central zone of phase‐encoding plane while sparse sampling its periphery, which results in the formation of sparsely sampled MR raw data. This research compares the performance of image reconstruction from sparsely sampled MR data by the often‐used zero filling (ZF) algorithm, and by two new methods, i.e., projection‐onto‐convex sets (POCS) and constrained transient error reconstruction approach (cTERA) algorithms. It is found that both the POCS and cTERA algorithms reconstruct high‐quality images that greatly improve the depiction of high‐frequency‐containing structures compared to ZF. However, POCS and cTERA take significantly increased computational times. Due to their intrinsic complexities compared to conventional Fourier transform and ZF reconstruction, POCS and cTERA algorithms are currently not implemented on commercial clinical MRscanners. It is also demonstrated that for a given scan time, it is possible to find an optimal specific sparse sampling strategies by both POCS and cTERA. Under pseudo optimal conditions, the corresponding POCS and cTERA images demonstrated better high‐resolution image quality compared to other, less optimal, sampling strategies. Therefore, it is desirable to acquire some high‐frequency data, as opposed to spending time only collecting an enlarged central region.
Sensitivity of Acoustic Wave Travel Times to Sound-Speed Perturbations in the Solar Interior

For time-distance helioseismology, it is important to establish the relationship between the travel times of acoustic waves propagating between different points on the solar surface through the solar interior and local perturbations to the sound speed in the propagation region. We use the Born approximation to derive a general expression for the linear sensitivity of travel times to local sound-speed perturbations in plane-parallel solar models with stochastic wave sources. The results show that the sensitivity of time-distance measurements to perturbations in sound speed depends on the details of the measurement procedure, such as the phase-speed filter used in typical time-distance data analysis. As a result, the details of the measurement procedure should be taken into account in the inversion of time-distance data. Otherwise, the inferred depths of perturbations may be incorrect.