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The idea of using polynomial methods to improve simple smoother iterations within a multigrid method for a symmetric positive definite system is revisited. A two‐level bound going back to Hackbusch is optimized by a very simple iteration, a close cousin of the Chebyshev semi‐iterative method, but based on the Chebyshev polynomials of the fourth instead of first kind. A full V‐cycle bound for general polynomial smoothers is derived using the V‐cycle theory of McCormick. The fourth‐kind Chebyshev iteration is quasi‐optimal for the V‐cycle bound. The optimal polynomials for the V‐cycle bound can be found numerically, achieving about an 18% lower error contraction factor bound than the fourth‐kind Chebyshev iteration, asymptotically as the number of smoothing steps k→∞$$ k\to \infty $$. Implementation of the optimized iteration is discussed, and the performance of the polynomial smoothers is illustrated with numerical examples. [ABSTRACT FROM AUTHOR]

We report the structural and magnetotransport properties of Cr-doped Bi2Te3 thin films deposited on Si(100) by the sputtering technique. The X-ray diffraction, Raman, and energy-dispersive X-ray analysis measurements suggest the possibility of intercalation of Cr atoms between the van der Waals gap of the two quintuple layers of c-axis-oriented Bi2Te3. The temperature-dependent resistivity trend of the Bi2Te3 specimen changed from metallic to insulating behavior when doped with Cr. The suppression of weak anti-localization and electron–electron interaction effects is observed in the magneto-transport behavior of the Cr-doped sample. After doping of Bi2Te3 with Cr, the calculated parameters such as pre-factor ( α) , Berry Phase φ B , and slope of temperature-dependent conductivity correction κ changed from non-zero to zero value while mass term (m ) changed from ~ zero (i.e., massless case) to one (i.e., massive case). The estimated values of topological parameters provide evidence of the transition from massless to massive Dirac characteristics of charge carriers when sputtered Bi2Te3 topological insulator films are doped with Cr. Thus, the study demonstrates that the magneto-transport measurements can be used to probe non-trivial transport characteristics of topological materials and also paves the way to fabricate functionalized topological materials by an industrial-friendly deposition technique such as sputtering. [ABSTRACT FROM AUTHOR]

The dynamic stability derivatives of flight vehicle are directly related to unsteady aerodynamics during maneuverability, and are considered as key parameters to both the aerodynamics, control system design and flight qualities evaluation. As the rapid development of new conceptual aircraft configurations, higher precision and efficiency calculations of the dynamic stability derivatives are urgently required. Limited by high costs and risks, the traditional experimental ways of flight test and wind tunnel test cannot be widely used, thus the numerical calculation on dynamic stability derivatives have become the primarily approaches. This paper reviews the numerically methods applied in the estimation of aircraft dynamic stability derivatives, includes the early analytical method, the empirical and semi-empirical methods and the widely used modern time domain and frequency domain methods, deeply highlighting the advantages and drawbacks of these methods of the actual applications on various aircrafts. The early analytical method by using potential theory can be used to calculate dynamic stability derivatives and will never work for current geometries. The empirical and semi-empirical methods are available with simple mathematical model and existed data. They have the advantage to be simple and rapid to compute and can be well adapted for initial evaluation of aircraft conceptual design. The time domain analysis based on solving Euler or NS equations with CFD technique are the most widely used methods to obtain the aircraft dynamic stability derivatives. With a variety of different strategies, they can calculate the combined and single dynamic derivatives to satisfy the demand of aircraft design in each stage. Even they are accurate and better in adaptability, the huge time cost on the periodic unsteady flow limits the application. To overcome this problem, the frequency domain methods based on harmonic oscillation are developed. They only use the results at several sample points during the unsteady cycle to reconstruct the periodic unsteady flows to further efficiently obtain the dynamic stability derivatives. These frequency domain methods are currently available only in harmonic oscillation cases. This paper also discusses and analyses the existing problems and possible development directions of the numerical methods to calculate aircraft dynamic stability derivatives from four aspects: theory, calculating elaboration, efficiency and accuracy, and application. [ABSTRACT FROM AUTHOR]

Recently it has been proposed that the long-range electronic order formed by trimerons in magnetite should be frustrated due to the great degeneracy of arrangements linking trimerons. This result has important consequences as charge ordering from the condensed minority band electrons leads to a complex 3D antiferro orbital order pattern. Further more, the corner sharing tetrahedra structure of spinel B-sites supports frustration for antiferromagnetic alignments. Therefore frustration due to competing interactions will itself induce disorder and very likely frustration in the spin orientations. Here we present very low temperature specific heat data that show two deviations to the magnons and phonons contributions, that we analyze in terms of Schottky-type anomalies. The first one is associated with the thermal activation across both ferroelastic twin and ferromagnetic anti-phase domains. The second Schottky-type anomaly displays an inverse (1/H) field dependence which is a direct indication of the disordered glassy network with macroscopically degenerated singular ground states. [ABSTRACT FROM AUTHOR]

The static aeroelastic torsion divergence problem is the main obstacle to bring forward swept wing into massive applications. The aeroelastic tailoring technique-based radial basis function neural networks (RBFNNs) and genetic algorithm (GA) optimization in MATLAB considering the material orientation, thickness, and lay-up are elucidated in the present work. RBFNNs are used to build a surrogate model between the composite parameters and structure displacement, which is proved robust and accurate. Then an optimal structure is obtained by GA global search based on RBFNNs model with the weight constrain. The displacements of the forward swept wing caused by an approximate aerodynamic load are decreased 32.5% through finite element method (FEM) static structural analysis. The modal analysis illustrates that the first mode frequency increases by 33.0% and the second mode increases by 37.9%. A computational aeroelasticity approach is developed by in-house Hybrid Unstructured Reynolds-Averaged Navier-Stokes solver associating an open source FEM code – Calculix. The results of coupling calculations show effectiveness of aeroelastic tailoring optimization of composite forward swept wing without weight penalty. The results obtained demonstrate that for the forward swept wing, the most violent situation appears around Mach Number 1.0 where the aeroelastic tailoring optimization could decrease the torsion angle by nearly 70.0%. The torsion of forward swept wing will increase at subsonic and decrease at supersonic with the increase of velocity. [ABSTRACT FROM AUTHOR]

The first-principles density functional theory calculations have been used to investigate the relation between magnetic and structural properties of LuFe2O4 for both the charge-ordered (CO) and the mixed-valence (MV) phases and also to compare the electronic properties for both phases. The computed structural parameters of rhombohedral and monoclinic systems are found to be in good agreement with experimental findings. An analysis of the magnetic properties is provided considering nonmagnetic, ferromagnetic, antiferromagnetic, and ferrimagnetic model orderings. In agreement with experimental results, CO modification of LuFe2O4 is predicted to be ferrimagnetic. The GGA + U electronic structures show a semiconducting behavior of CO phase while a metallic character for MV LuFe2O4 phase. [ABSTRACT FROM AUTHOR]

Tiltrotor aircraft are equipped with large rotors, usually driven by heavy engines in nacelles located at the tip of the wings. This combination of large rotors and high masses on wings which form a relatively elastic support makes whirl flutter a critical phenomenon for the design of the aircraft and its performance. In this article, a multibody-based simulation model of a tiltrotor wind tunnel model is presented, combining a mixed finite element/multibody representation of the support, a detailed kinematic model of the rotor hub and a strip-wise definition of air loads on the blades. Investigations on the effect of parameter changes and non-linearities on the calculation of the aeroelastic stability boundary are executed. The selected operational points are taken from wind tunnel experiments performed by a consortium of partners in the course of the European ADYN project. The regarded wind tunnel model is a half model of a tiltrotor wing, simplified for the use in whirl flutter investigations. The rotor is four-bladed; the rotor hub is of a gimbal type. Structural dynamics properties of the model are known from detailed experimental investigations. Numerical analyses of the dynamic behaviour of the model are performed in the frequency and in the time domain. Results show considerable differences for linear and non-linear models. This paper describes the simulation approach, the model setup and the comparison of the data with selected experimental results. [ABSTRACT FROM AUTHOR]

This paper deals with the mechanical concept of a whirl flutter aeroelastic demonstrator. It works out the previous study on the W-WING demonstrator design and summarises the new achievements. The paper gives a theoretical background of the subjected whirl flutter phenomenon and summarises the whirl flutter occurrence in aerospace practice. The second part is focused on the experimental research of whirl flutter. At first, a brief summary of past main developments in this field is provided. The main part deals with the new aeroelastic demonstrator ‘W-WING’, designed and developed at the VZLU. The demonstrator represents wing and engine of a twin turboprop commuter aircraft. Contrary to the most of past demonstrators, it includes thrusting propeller. The demonstrator allows changes of the main structural parameters influencing whirl flutter stability characteristics. The demonstrator is intended for experimental investigations at the VZLU 3m-diameter low-speed wind tunnel. The results will be used for validation of analytical methods and software tools as well as in the frame of research projects. [ABSTRACT FROM AUTHOR]

Conventional buffet onset methods for a 2D supercritical airfoil, SC0410, in transonic regime for various Mach number and various angles of attack have been surveyed. The existing methods give good results for high subsonic and transonic regimes, but demand a computational procedure to detect the buffet onset. One of these methods, trailing edge pressure divergence, that have been recognized inappropriate in other studies for supercritical airfoils, shows acceptable result at least for the present supercritical airfoil. A new method has been proposed by the authors for transonic regime that is based on the physical definition of the buffet onset from the surface pressure distribution diagram. This method does not require any special calculations. The data scrutiny shows good agreement by this method in comparison with the conventional schemes. [ABSTRACT FROM PUBLISHER]

TbMnO nanoparticles were prepared by hydrothermal process with combination of post-annealing at different temperatures. Thermal, XRD, and FT-IR analysis confirms the formation of TbMnO phase. The morphology and particle size of the samples were determined using HRSEM and HRTEM. The prepared TbMnO sample shows average particle size in the range of 40-60 nm. XPS analysis confirms the oxidation state of the samples. The dc magnetic susceptibility measurements in an applied magnetic field 50 Oe of TbMnO samples annealed at 800 and 900 °C show anti-ferromagnetic to paramagnetic transition at 80 and 86 K, respectively, which is also confirmed by magnetic hysteresis loops in the temperature range from 5 to 300 K. The size, morphology, and magnetic property of the nanoparticles were dependent on annealing temperatures. [ABSTRACT FROM AUTHOR]

The article discusses the tripartite soteriology developed by Eusebius of Caesarea in response to Porphyrian universalism. It examines work of Porphyry an anti-Christian writer in search for universalism he devised from a hierarchical, tripartite soteriology of the Neoplatonic concepts. Meanwhile, Eusebius Caesarea in both his "Praeparatio evangelica" (PE) and Demonstratio evangelica (DE) responded to the charges that Christianity as a new religion lacks the authenticity of an ancient tradition. Moreover, Eusebius apologetic works resulted a confidence that Christian universalism is an important cause for the success of the Church.

Objective: To review persons charged or convicted with homicide referred to the Western Australian Forensic Psychiatric Service. Method: Review of case note of referrals over a five-year period. Results: Data from 42 cases were collected. Offenders and victims belonged to a variety of ethnic backgrounds. There were four cases of multiple homicide. The majority of perpetrators and victims were males. A significant number had a pre-existing major psychiatric disorder, about half of who were under psychiatric care at the time of the offence. Half of the patients were diagnosed with schizophrenia or delusional disorder. A gun was used in one fifth of the cases. Conclusions: The survey highlights the importance of risk management and assertive community follow-up in those with psychosis. [ABSTRACT FROM AUTHOR]

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