[en] The stability of kinetic toroidal Alfven waves with multi-gap coupling is analyzed by using the two-dimensional ballooning transform. An alternate convergence scheme, based on the smallness of the inverse aspect ratio, is devised. The resulting wave functions are oscillatory and do not balloon in contrast to the wave functions of conventional ballooning theory. It is shown that the single-gap theory is a special, weak shear (s → 0) limit of the formalism. Analytical and numerical results for the two fundamental branches, the ideal toroidal Alfven eigenmode (TAE), and the kinetic toroidal Alfven eigenmode (KTAE) are presented and discussed

[en] A perturbation theory based on the two dimensional (2D) ballooning transform is systematically developed for ideal toroidal Alfven eigenmodes (TAEs). A formula, similar to the Fermi golden rule for decaying systems in quantum mechanics, is derived for the continuum damping rate of the TAE; the decay (damping) rate is expressed explicitly in terms of the coupling of the TAE to the continuum spectrum. Numerical results are compared with previous calculations. It is found that in some narrow intervals of the parameter mε the damping rate varies very rapidly. These regions correspond precisely to the root missing intervals of the numerical solution by Rosenbluth et al

[en] By systematically doing the higher order theory, the predictions of the conventional ballooning theory (CBT) are examined for non-ideal systems. For the complex solvability condition to be satisfied, radial variation of the lowest order mode amplitude needs to be invoked. It turns out, however, that even this procedure with its concomitant modifications of eigenvalues and eigenstructures, is not sufficient to justify the predictions of many CBT solutions; only a small set of CBT solutions could be put on a firm footing. To demonstrate our general conclusions, theoretical and numerical results are presented for system of fluid drift waves non-adiabatic electron response

[en] Microstructure of TiAl produced by Laser Engineered Net Shaping (LENS) has been characterized using optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has been shown that the substrate has a significant effect on the microstructure deposited. Depending on operational parameters, either equiaxed γ-TiAl/α₂-Ti₃Al or single phase α₂ microstructure can be obtained. In-situ heating experiments reveal that nucleation of lamellae often starts at grain boundaries in this retained α₂ grains. By careful control of post heat treatment, an ultra fine lamellar microstructure may be obtained, which may significantly improve tensile property in these alloys

No abstract available

[en] Using the tight-binding Hamiltonian approach, we comparatively investigate the energy spectrums of triangular zigzag phosphorene quantum dots (PQDs) and rings (PQRs), as well as their potential applications. In comparison with the outer edge states in the PQD, new extra inner edge states can be produced in the PQR by its internal hole. A transition from the uncoupled to coupled edge states can be induced by decreasing the width between the outer and inner edges of the PQR. Also, the edge states in PQD/PQR are all anisotropically localized in one side, rather than three sides as in triangular graphene quantum dots (QDs) and rings (QRs). Furthermore, the PQD/PQR energy levels can be anisotropically manipulated by the external electric fields and strains, clearly demonstrating their potential applications in field effect transistors or electromechanical devices. In the meanwhile, we also consider the electron probability distributions corresponding to the different energy levels, clearly exposing the characteristics of the PQD/PQR energy levels. The comparison between the asymmetrical triangular PQDs/PQRs and the symmetrical triangular QDs/QRs in graphene should be instructive for understanding the similar triangular QDs/QRs in other two-dimensional layered materials, as well as other types of QDs/QRs of different shapes. - Highlights: • We make a comparative study on the energy levels of the phosphorene quantum dots and rings. • The energy levels can be anisotropically controlled by the electric field and the strains, different from those in graphene counterparts. • The edge states in phosphorene triangular quantum dot and rings are anisotropic. • A helpful reference for understanding phosphorene nanostructures of other shapes and designing devices.

[en] The resistivity, electron paramagnetic resonance (EPR) and microstructure of polycrystallines Ru_1-xSb_xSr₂Gd_1.4Ce_0.6Cu₂O_10-δ (x=0, 0.01, 0.02, 0.05, 0.07) have been studied systematically. Sb doping reduces the conductivity of the system and the onset superconducting transition temperature decreases from 42 K for x=0 to 19 K for x=0.07. This may reflect the increase in hole localization due to a distortion of RuO₆ octahedra. The temperature dependencies of magnetic resonance for samples Ru_1-xSb_xSr₂Gd_1.4Ce_0.6Cu₂O_10-δ show that there are two absorption peaks. The first one around the magnetic field 3300 Oe corresponds to the EPR of the Gd ions, and the second that appears below the ferromagnetic transition temperature is a ferromagnetic resonance due to the ordered Ru ions

[en] Based on the tight-binding Hamiltonian approach, we demonstrate that the electromechanical field effect transistors (FETs) can be realized by using the multilayer phosphorene nanoribbons (PNRs). The synergistic combination of the electric field and the external strains can establish the on–off switching since the electric field can shift or split the energy band, and the mechanical strains can widen or narrow the band widths. This kind of multilayer PNR FETs, much solider than the monolayer PNR one and more easily biased by different electric fields, has more transport channels consequently leading to the higher on–off current ratio or the higher sensitivity to the electric fields. Meanwhile, the strain-induced band-flattening will be beneficial for improving the flexibility in designing the electromechanical FETs. In addition, such electromechanical FETs can act as strain-controlled FETs or mechanical detectors for detecting the strains, indicating their potential applications in nano- and micro-electromechanical fields. - Highlights: • Electromechanical transistors are designed with multilayer phosphorene nanoribbons. • Electromechanical synergistic effect can establish the on–off switching more flexibly. • Multilayer transistors, solider and more easily biased, has more transport channels. • Electromechanical transistors can act as strain-controlled transistors or mechanical detectors.

[en] Phase transformations and structural morphologies of Ti-50Al-2Mn-2Nb alloy have been studied. It has been shown that the prior structures and cooling rates influence the two phase transformations, γ → α during heating, and α → γ during cooling. Mixed phase morphologies have been observed when cooling from the single α phase region which involve different mechanisms of formation of γ phase. These observations are discussed in terms of phase transformations of TiAl alloys

[en] The collision effect of cross-field transport in a radial electric field for ions and electrons is studied and the transport equations are obtained, leading to a better understanding of the relation of collision effect with a radial electric field. The collisional transport equations indicate that there is a radial current generated by the damping of ExB drift. This current is in the direction of the radial electric field, so it will reduce the radial electric field and is unfavorable for forming the H mode. (author)