Electrodynamics in superconductors explained by Proca equations\nA fully consistent model to study electrodynamics for superconductors in the stationary and non-stationary regimes has been developed based on Proca equations and a massive photon. In particular, this approach has been applied to study the electric field penetration depth in superconductors. The model shows a deviation from the charge contribution to an internal electric field compared to previous approaches.
Fatigue and fracture behavior of bulk metallic glasses and their composites\n\u00a9 2018 Elsevier Ltd A fundamental understanding of the fatigue and fracture behavior of bulk metallic glasses (BMGs) and their composites is of critical significance for designing new BMG systems and developing new manufacturing and processing techniques so as to broaden the scope of applications of BMGs and their composites. However, the fatigue and fracture studies on BMGs are limited so far, compared to other mechanical properties. The present work reviews the fatigue and fracture behavior of BMGs and their composites, as well as that of metallic-glass films, ribbons, and wires. The grand challenge for the fatigue and fracture performance of BMGs is: What produces a large difference among the fatigue and fracture results of BMGs? According to the fatigue and fracture investigations of crystalline alloys including recently invented high entropy alloys, many factors could be involved, such as the composition, material quality, specimen geometry, chemical environment, surface condition, temperature, cyclic frequency, mean stress, and residual stress, etc. Based on this challenge, the present work will review and address the factors affecting the fatigue and fracture behavior of BMGs and their composites. Furthermore, the mechanisms of fatigue-crack initiation, propagation, and fracture of BMGs and their composites in different loading conditions and environments will be outlined, analyzed, and discussed. Future research directions of fatigue and fracture of BMGs and their composites are provided for reference.
Impurity-controlled film growth and elastic properties of CoCrCuFeNi thin films\nThe growth mode during physical vapor deposition of metallic thin films is very sensitive to the presence of impurity species. These impurities can originate from the residual ambient gases present in the vacuum chamber and usually impede continued crystal growth by inducing renucleation. During magnetron sputtering at intermediary base pressures (~10\u22124Pa), the effect of these impurities can be estimated from the ratio of the impurity flux to the metallic flux. In this study, the influence of the ambient impurity flux on the growth mode of CoCrCuFeNi High-Entropy Alloy (HEA) thin films is investigated. It is shown that the impurity-to-metal flux ratio effectively controls the texture, grain size, porosity, and elastic properties of the nanocrystalline CoCrCuFeNi thin films. A less clear (111) fiber texture is observed at higher impurity-to-metal flux ratio. With increasing impurity-to-metal flux ratio the grain size decreases while the porosity increases. The elastic constants, and Young's modulus for CoCrCuFeNi is reported to be the highest for the \u3008111\u3009 direction. Hence, the change in film texture also affects the elastic constants and Young's modulus which tend to become lower as more grains with different orientation are observed at higher flux ratios. This study demonstrates that an exact knowledge of the impurity-to-metal flux ratio, or otherwise stated, of the base pressure and deposition rate during sputter deposition is imperative for the synthesis of HEA films with reproducible properties.
New solid-state electric double-layer capacitor using poly(vinyl alcohol)-based polymer solid electrolyte\nPoly vinyl alcohol (PVA) dissolves large amounts of lithium salts (up to about 1.5 g/g of PVA) such as LiCF3SO3, LiClO4 and LiBF4 in its polymer matrix. The composites obtained show good ionic conductivity. When the PVA-lithium salt composites are used as the solid electrolyte in solid-state electric double-layer capacitors with porous and electrically conducting claycarbon composites as polarizable electrodes, the solid-state electric double-layer capacitors show good charge/discharge behavior with large capacitance of 2.5-3.5 F/(cm3 of the capacitor).
Structural phase transition and electronic properties of CaO under high pressure\n\u00a9 2018 IOP Publishing Ltd. The crystal structure of the CaO compound is studied up to 300 GPa under high hydrostatic pressure using the density functional theory (DFT) with the generalized gradient approximation (GGA). Pressure-volume relationships, structural transitions and electronic properties in CaO compound are investigated using Siesta method. CaO crystallizes in the NaCl-type (B1) structure (space group: Fm3m ) in ambient conditions. CaO transforms from this structure to CsCl-type (B2) structure (space group:Pm3m) at high pressure. This transformation is based on a intermediate state with space group R3m. Moreover, the electronic band structures of the B1 and B2 structures of CaO have been calculated. According to this calculation, obtained band gap values are in good agreement with the values reported in the literature.
Extended Supersymmetry in Four-Dimensional Euclidean Space\nSince the generators of the two SU(2) groups which comprise SO(4) are not Hermitian conjugates of each other, the simplest supersymmetry algebra in four-dimensional Euclidean space more closely resembles the N=2 than the N=1 supersymmetry algebra in four-dimensional Minkowski space. An extended supersymmetry algebra in four-dimensional Euclidean space is considered in this paper; its structure resembles that of N=4 supersymmetry in four-dimensional Minkowski space. The relationship of this algebra to the algebra found by dimensionally reducing the N=1 supersymmetry algebra in ten-dimensional Euclidean space to four-dimensional Euclidean space is examined. The dimensional reduction of N=1 super Yang\u2013Mills theory in ten-dimensional Minkowski space to four-dimensional Euclidean space is also considered.
An overview of ionosphere-thermosphere models available for space weather purposes\nOur objective is to review recent advances in ionospheric and thermospheric modeling that aim at supporting space weather services. The emphasis is placed on achievements of European research groups involved in the COST Action 724. Ionospheric and thermospheric modeling on time scales ranging from a few minutes to several days is fundamental for predicting space weather effects on the Earth's ionosphere and thermosphere. Space weather affects telecommunications, navigation and positioning systems, radars, and technology in space. We start with an overview of the physical effects of space weather on the upper atmosphere and on systems operating at this regime. Recent research on drivers and development of proxies applied to support space weather modeling efforts are presented, with emphasis on solar radiation indices, solar wind drivers and ionospheric indices. The models are discussed in groups corresponding to the physical effects they are dealing with, i.e. bottomside ionospheric effects, trans-ionospheric effects, neutral density and scale height variations, and spectacular space weather effects such as auroral emissions. Another group of models dealing with global circulation are presented here to demonstrate 3D modeling of the space environment. Where possible we present results concerning comparison of the models' performance belonging to the same group. Finally we give an overview of European systems providing products for the specification and forecasting of space weather effects on the upper atmosphere, which have implemented operational versions of several ionospheric and thermospheric models.